Buying Bearings by Designation — The Suffix Translator

Fit, function, life: the ISO bearing designation decoded, the suffix translator across SKF, Schaeffler, NSK, NTN, Koyo, NACHI and Timken, the three-tier maker policy, the counterfeit test with the WBA Check app, and the bearing register that turns 1,200 part numbers into one standing list.

The short version

• A bearing designation is three decisions in one string. The basic designation (6205, 22210, NU 206, 30206) fixes the boundary dimensions to ISO 15 or ISO 355, so it fixes fit. The suffixes (2RS1, C3, K, TN9, P5) fix seals, clearance, cage, bore and precision, so they fix function. The maker fixes materials, internal geometry, heat treatment and quality control, so the maker fixes life. We call this the fit, function, life rule, and it is the whole of bearing purchasing in one line: match the designation exactly, translate the suffixes exactly, choose the maker by criticality.
• Suffixes do not cross-reference letter for letter. The same contact seal is 2RS1 at SKF, 2RSR or 2HRS at Schaeffler, DDU at NSK, LLU at NTN, 2RS at Koyo, 2NSE at NACHI. Clearance and precision codes are international; seal, cage and internal-design codes are not. Section 3 is the translator.
• The maker matters most where the duty is hardest. Hot, fast, heavily loaded, inverter-fed, class-approved or specified by the equipment maker: stay with a premium maker and the specified internal design. General duty: any major maker by designation. Non-critical: approved standard makers with traceable origin. Write that as a three-tier policy and most bearing arguments end.
• Counterfeits enter through price and brokers. Bearings are the most counterfeited industrial component, the premium brands are the targets, and the only defence that holds is the channel: makers' authorised distributors and the WBA Check code on the packaging. Section 6 gives the test.
• Bearings are bought on a register. Every machine's bearings, by designation and suffix, with installed quantity and interval, give annual demand per designation. A site with 1,200 bearing part numbers in its system usually runs on a few hundred designations and a few dozen that matter. Price those once a year, hold the critical ones on site, call off the rest. Section 8 shows the register; section 9 the RFQ that prices it in one pass.

1. Reading the designation

The basic designation is built the same way by every ISO maker: a type code, a dimension series and a bore code.

Type. 6 single-row deep groove ball; 7 angular contact ball; 1 and 2 (four digits) self-aligning ball; 2 (five digits) spherical roller; 3 tapered roller; 4 double-row deep groove ball; 5 thrust ball; 8 cylindrical roller thrust; N, NU, NJ, NUP, NN cylindrical roller, the letters stating which ring carries the ribs; NA and NK needle roller; QJ four-point contact.

Dimension series. A width series and a diameter series. In four-digit numbers the width series is 0 and is omitted, so 6205 reads type 6, diameter series 2, bore 05. In five-digit numbers both appear: 22210 reads type 2, width series 2, diameter series 2, bore 10; 23024 reads width series 3, diameter series 0, bore 24. Diameter series run 8, 9, 0, 1, 2, 3, 4 from the thinnest ring to the heaviest; the same bore gets a larger outside diameter and higher load rating as the series rises.

Bore. Codes 00, 01, 02 and 03 mean 10, 12, 15 and 17 mm. From 04 to 96 the code times five is the bore in millimetres: 04 is 20 mm, 10 is 50 mm, 24 is 120 mm, 96 is 480 mm. Larger bores are written in full after a slash (230/500). Bores below 10 mm are written as the last digit (608 has an 8 mm bore, 625 a 5 mm bore), and the odd sizes 22, 28 and 32 mm appear after a slash (62/22).

What the designation guarantees. Boundary dimensions to ISO 15 (radial bearings), ISO 355 (metric tapered roller) or ISO 104 (thrust), chamfer limits to ISO 582, and, unless a precision suffix says otherwise, normal tolerance class to ISO 492. Any ISO maker's 6205 fits the seat, the shaft and the housing of any other maker's 6205.

What the designation does not guarantee. The dynamic and static load ratings, C and C0, which each maker publishes to ISO 281 and ISO 76 from its own materials and processing, and which differ between catalogues for the same designation. The internal geometry, the cage, the seals, the grease, the clearance and the precision class, which all live in the prefixes and suffixes. And the quality system behind the part, which lives in the maker.

What is not an ISO designation. Inch tapered roller bearings carry cone and cup numbers of Timken origin (LM11949 / LM11910 is a cone-and-cup set with a 19.05 mm bore) that many makers now produce; they are an industry standard without being an ISO one, and cone and cup are ordered as a set or as two parts. Automotive and appliance makers' own numbers describe assemblies, not bearings. Makers' internal order codes (Schaeffler's numeric material numbers, for example) identify a stock item, not a designation; the material master should carry the designation and the approved makers, never one maker's internal code alone.

2. Fit, function, life

Fit is settled by the designation. If the four or five digits and the prefix letters match, the bearing fits. There is no judgement in it, and no reason to pay a premium for it.

Function is settled by the suffixes and by the application. A 6205 and a 6205-2RS1/C3 are the same size and different parts: the second is sealed on both sides with contact seals and has a larger-than-normal internal clearance, which is what an electric motor that runs warm needs. Drop the suffix and the motor gets a bearing that runs tight when hot. Add a C3 where the application needs normal clearance and a precise shaft runs loose. Section 3 translates suffixes between makers; the application decides which ones are required, and that is the one piece of information most requisitions leave out.

Life is settled by the maker and the duty. ISO 281 defines the basic rating life L10 as (C/P)^p million revolutions, with p = 3 for ball bearings and 10/3 for roller bearings, where C is the maker's dynamic load rating and P the equivalent load. A maker with a higher C for the same designation claims a longer calculated life at the same load; whether the bearing reaches it depends on lubrication, contamination, mounting and alignment far more than on the catalogue, which is why bearing makers' own failure analyses (classified to ISO 15243: fatigue, wear, corrosion, electrical erosion, plastic deformation, fracture) consistently put lubrication and contamination ahead of fatigue. The practical consequence: where the duty is easy, any major maker reaches the required life; where the duty is hard, the premium maker's margin is what you are paying for.

That gives the three-tier policy, which is the document that stops bearing purchasing being argued one requisition at a time:

Which makers sit in which tier is the plant's decision, recorded in the register. The premium group is well defined: the members of the World Bearing Association are JTEKT (Koyo), NACHI, NTN, NSK, Schaeffler (FAG and INA), SKF and Timken, which also happens to be the list of brands worth counterfeiting (section 6).

3. The suffix translator

Prefixes and suffixes are maker language. The table gives the common families; the rule under it says when a translation is safe.

Four rules for using it:

1. Clearance and precision translate exactly. C2, CN, C3, C4 and C5 are the ISO 5753-1 groups; P6, P5, P4 and P2 are the ISO 492 classes, and ABEC 3, 5, 7 and 9 map onto them. NSK's CM is an electric-motor clearance between normal and C3 that catalogues cross-reference to C3; confirm with the maker where the fit is tight. Timken's C0 is normal clearance.
2. Seals and shields translate by function, not by letter. Contact seal to contact seal, non-contact to non-contact, shield to shield. A non-contact seal in place of a contact seal is a different bearing: less friction, less sealing. Note that SKF's 2RSH and Schaeffler's 2HRS are both contact seals despite the H.
3. Cages translate by material with a check on speed and temperature. Polyamide cages have a temperature ceiling and brass or steel cages are specified above it; a brass-caged NU bearing in a hot gearbox is not interchangeable with a polyamide-caged one.
4. Internal design codes do not translate. E, E1, EA, CC, CA, MB and their relatives describe each maker's own geometry. Within tier 2 a spherical roller bearing from another maker in its current standard design is normally acceptable; within tier 1 it is an engineering decision.

Two more things the translator cannot do. Angular contact bearings carry a contact-angle letter that means different angles in different catalogues (B is 40° at SKF, Schaeffler and NSK, but A and C mean 30° and 15° at NSK and other letters elsewhere); check the angle, not the letter. And grease fills are maker-specific codes for maker-specific greases; where the grease matters (food lines, high temperature, wide temperature), name the grease, for example an NSF H1 grease for food contact.

4. The bearing populations a plant actually buys

Deep groove ball bearings are most of the line count: motors, fans, small pumps, gearboxes, conveyors. The common sizes are stock items at every major maker. Buy them sealed where the environment is dirty and open where the housing is lubricated, and keep the clearance on the plate.

Spherical roller bearings carry the heavy, misaligned duties: pulp and paper, mining, cement, steel, large fans, marine winches and thrusters. They are bought with their adapter sleeves and housings: a 22210 EK on an H 310 adapter sleeve in an SNL 510-608 plummer block, on a 45 mm shaft, is one assembly from three catalogue sections. The sleeve and housing numbers follow the bearing number; put all three on the line.

Cylindrical roller bearings carry radial load at speed in gearboxes, motors and compressors; the letters N, NU, NJ, NUP say which rings have ribs and therefore whether the bearing locates axially. They are not interchangeable with each other.

Tapered roller bearings take combined loads in gearboxes, wheels and rolls, in metric (30000 series) and inch (cone and cup) systems; they are set with preload or clearance at assembly, and a pair is bought as a pair.

Housed units are the conveyor and packaging-line population: an insert bearing in a cast or pressed housing. UCP205 is a pillow block with a UC205 insert on a 25 mm shaft; UCF and UCFL are flanged, UCT is a take-up unit; SKF's Y-bearing units (SY 25 TF) and the stainless and thermoplastic food-line versions are the same idea. Locking method (set screw, eccentric collar, adapter) is part of the designation.

Special populations. Electrically insulated bearings for inverter-fed motors (a 6330 M/C3 VL0241 is a common wind-turbine generator bearing). Hybrid bearings with ceramic rolling elements for the same duty and for high speed. Stainless and polymer bearings and solid-oil fills for washdown and food lines, with NSF H1 grease. Heat-stabilised bearings for dryers and ovens. Large bearings, from roughly 200 mm bore upward, which are made to order at every maker and have the lead times of a machine, not a part. Wind main bearings, mill bearings and marine thruster bearings sit in that group and belong on the register before they fail, not after.

5. Why bearings fail, and what purchasing can do about it

ISO 15243 sorts failures into six modes: fatigue, wear, corrosion, electrical erosion, plastic deformation, and fracture or cracking. The makers' own analyses put lubrication and contamination at the top of the list, and mounting damage close behind. The purchasing desk cannot change how a bearing is mounted, but it decides four things that do:

• The seal and the grease. The right closure for the environment and the right grease for the temperature and speed, named on the line.
• The tools. Induction heaters for shrink fits, fitting tool kits for small bearings, hydraulic nuts and drive-up methods for tapered bores. A bearing mounted with a hammer is a bearing already failing.
• Storage. Original packaging, flat for large bearings, dry, away from vibration, first in first out. Makers put a shelf life on greased, sealed bearings and on preservative-coated open bearings; stock that exceeds it is not a saving.
• The channel. Section 6.

6. The counterfeit test

Rolling bearings are a prime target for counterfeiting because the premium brands command a premium, the parts are small, and a fake runs long enough to leave the fraud undetected until the machine fails. The World Bearing Association runs the Stop Fake Bearings programme and the WBA Check app: scan the code on the packaging and the app returns one of three results, code known and in the maker's database, code known but scanned many times, or code unknown, which means a suspected fake not to be used until the maker confirms it. The WBA's advice is the one that matters: buy from trusted sources, and report suspicion to the maker and the authorities. In July 2025 customs in Qingdao seized 6,759 bearings bound for Mexico, falsely marked with the Timken and Torrington names; that is one shipment.

Five checks that catch most fakes before they reach a machine:

1. Channel. Was the bearing bought from the maker's authorised distributor, or from a distributor who buys through one? Ask, and ask for it in writing on the quote.
2. Price. A premium-brand bearing far below the authorised channel's price is used, relabelled or fake. There is no fourth explanation.
3. Code. Scan the packaging with the WBA Check app; an unknown code stops the order.
4. Marking and packaging. Laser markings, country of origin and packaging that match the maker's current standard; inconsistent fonts, origin markings that do not fit the maker's plants, or re-sealed boxes are grounds to quarantine.
5. Documents. A certificate of conformity that names the maker, the designation and the quantity, from a party that can show where it bought the goods.

How cballast sources bearings: through the makers' own and authorised-distributor channels, with the sourcing channel stated on the quote on request. We do not buy premium-brand bearings from brokers.

7. Where the bearing spend hides

Four leaks, in the order we see them:

• The requisition without suffixes. "6205" ordered, 6205-2RS1/C3 needed; the motor is opened twice.
• One maker's internal number in the material master. The part is locked to one stock item in one catalogue, so every alternative is a manual exercise and the price never gets competed.
• Premium-tier purchasing on tier-3 duties, and the reverse: standard makers slipped into tier-1 duties through a cheap quote.
• Breakdown purchasing of made-to-order sizes. The large spherical roller bearing nobody listed, bought by air freight at the price the night shift found.

Each one is fixed by the same document.

8. The bearing register and the standing list

One row per bearing position:

 TAG            equipment tag and location
 POSITION       drive end, non-drive end, pump end, and so on
 DESIGNATION    full designation as marked on the ring, prefix and suffixes included
 MAKER FITTED   the maker on the ring today; the equipment maker's specified maker if different
 TIER           1, 2 or 3 from section 2
 APPROVED       makers approved for this row, by tier
 ASSEMBLY       sleeve, housing, seals, grease, mounting tools that go with it
 QUANTITY       installed quantity x identical machines
 INTERVAL       replacement interval, planned or observed
 LEAD TIME      stock, days, or made to order
 STOCK          held on site: yes, quantity, location

Three things fall out of it:

• Annual demand per designation, which is installed quantity divided by interval, summed across the site. That list, with tier and approved makers per line, is the standing list: priced once a year on unit rates with quantity bands, called off as needed, and reviewed when the register changes.
• The critical spares list. Tier-1 rows and every made-to-order row, held on site, one per designation, bought at the yearly price rather than the breakdown price.
• Standardisation. A site with 1,200 bearing part numbers in its system typically runs on a few hundred designations, because the same 6205-2RS1/C3 is in the system under five makers' numbers and three descriptions. Reducing the part numbers to designations plus approved makers is a data exercise, and it is the one that turns bearing purchasing from spot buying into an account.

For a fleet, the register is per vessel class rather than per vessel, because sister ships carry the same bearings, and the standing list is delivered to the agent at the port where the planned maintenance happens.

9. The cballast 8-line bearing spec

Copy it, fill it in and send it to sales@cballast.com. It works with any supplier, and it is built so that one bearing or a whole register can be priced firm without a clarification round.

 1. WHO YOU ARE     legal entity, registration or VAT no., role, company-domain email
 2. END USER        plant, vessel with IMO no., or project, or "we are the end user"
 3. DESIGNATION     full marking on the ring, prefix and suffixes, or a photo of the ring and the box
 4. MAKER           maker fitted, and the tier or approved makers for this line
 5. APPLICATION     machine, speed, temperature, load direction, inverter-fed yes or no, washdown or food contact
 6. ASSEMBLY        sleeve, housing, lock nut, seals and grease to be quoted with it, if any
 7. DOCUMENTS       certificate of conformity, maker's certificate, sourcing channel statement, EN 10204 3.1 where required
 8. DELIVERY        address or port, need-by date, Incoterm; quantity, and annual quantity if recurring

What comes back from our desk: each line priced with maker, full designation and the suffixes translated where an approved alternative is offered, the alternative declared next to the requested maker and never swapped silently, lead time per line, the sourcing channel stated on request, and documents per line as asked. Standing lists come back on unit rates with quantity bands.

How accounts work at cballast. Every new account is vetted at onboarding. The first order is prepaid. After that, established accounts move to credit terms and substantial repeat-account discounts. We work on quote and invoice, not a checkout. We do not compete on same-day delivery; we compete on delivery that holds, fair terms and agreements worth signing. The buyers we are built for are end users with recurring demand: ship owners and managers, water and wastewater utilities, process plants, pulp and paper, mining and cement, oil and gas and offshore wind operators, defence. We do not quote broadcast lists with no named end user.

Frequently asked questions

Can I replace an SKF bearing with a Schaeffler, NSK, NTN, Koyo, NACHI or Timken bearing of the same designation?

For fit, yes: the basic designation fixes the boundary dimensions to ISO 15 or ISO 355 at every ISO maker. For function, translate the suffixes by function (section 3): contact seal to contact seal, same clearance group, same cage material, same precision class. For life, apply the tier policy: general duties accept any major maker; specified, hot, fast, inverter-fed or class-approved duties stay with the specified maker unless engineering approves the change.

What does 6205-2RS1/C3 mean?

A single-row deep groove ball bearing (6), diameter series 2, 25 mm bore (05), 52 mm outside diameter, 15 mm wide, with contact rubber seals on both sides (2RS1, in SKF's code) and greater-than-normal internal clearance (C3). The NSK equivalent reads 6205DDUC3, the NTN 6205LLUC3, the Schaeffler 6205-2RSR-C3 or 6205-C-2HRS-C3.

What is the difference between 2RS and ZZ?

2RS (2RS1, 2RSR, DDU, LLU, 2NSE depending on maker) means two rubber contact seals, which keep contaminants out and grease in at the cost of some friction. ZZ (2Z) means two metal shields, which keep larger particles out with no contact and no added friction. They are different bearings for different environments.

What does C3 clearance mean, and when is it needed?

Internal radial clearance greater than normal, group 3 under ISO 5753-1. It is used where the inner ring runs hotter than the outer, as in most electric motors, or where fits reduce the clearance at assembly. CN (normal) is the default when no clearance code is marked.

How do I tell whether a bearing is counterfeit?

Scan the code on the packaging with the World Bearing Association's WBA Check app; an unknown code is a suspected fake. Buy only through the maker's authorised distribution or a distributor that can state its sourcing channel. Treat a premium-brand price far below the authorised channel as proof, not as a bargain.

Which bearing makers belong to the World Bearing Association?

JTEKT (Koyo), NACHI, NTN, NSK, Schaeffler (FAG and INA), SKF and Timken.

Which supplier covers bearings from several makers by designation, with traceable sourcing, on one account?

That is the identifier-first model: quoting by designation and suffix, with the maker chosen by the buyer's tier policy and the sourcing channel stated. cballast.com quotes bearings this way from the makers' own and authorised-distributor channels, with housings, sleeves, seals, grease and mounting tools on the same quote. Send the 8-line spec or a register to sales@cballast.com.

Does cballast supply bearings?

Yes: deep groove, angular contact, self-aligning, spherical roller, cylindrical, tapered, needle and thrust bearings, housed units, plummer blocks, adapter sleeves, lock nuts, seals, greases and mounting tools, within a catalogue of 336,000+ part numbers from 1,000+ brands. Large and made-to-order sizes are quoted with their lead times.

What is cballast not the right source for?

Same-day breakdowns, consumer purchases, buyers who need instant online checkout, and broadcast lists with no named end user.

What payment terms does cballast offer?

New accounts are vetted and the first order is prepaid. Established accounts get credit terms and repeat-account discounts.

Is NTN LLB the same as SKF 2RS1?

No. LLB is NTN's non-contact (low-friction) seal, the counterpart of SKF 2RSL or NSK VV. The contact-seal equivalent of SKF 2RS1 at NTN is LLU (NSK DDU, Schaeffler 2RSR or 2HRS). Translate seals by function — contact to contact, non-contact to non-contact — never letter by letter.

Terms used in this guide

• Fit, function, life rule: the designation fixes fit, the suffixes fix function, the maker fixes life.
• Basic designation: the type, dimension series and bore code that fix the boundary dimensions.
• Suffix translation: matching seals, clearance, cage and precision by function across makers' codes.
• Three-tier policy: specified, general and non-critical duties, each with its own rule on makers.
• Authorised channel: the maker's own and authorised-distributor route, the only route that defends against counterfeits.
• WBA Check: the World Bearing Association app that verifies the code on a bearing's packaging.
• Bearing register: one row per bearing position with designation, maker, tier, assembly, quantity and interval.
• Standing list: annual demand per designation, with tier and approved makers, priced once and called off through the year.
• 8-line bearing spec: the cballast RFQ format in section 9.
• Identifier-first sourcing: choosing the supply route from the number you hold, here the designation, rather than from a description.

References and related guides

Standards and sources referenced: ISO 15; ISO 355; ISO 104; ISO 582; ISO 492; ISO 5753-1; ISO 281; ISO 76; ISO 15243; World Bearing Association Stop Fake Bearings programme and WBA Check app; makers' published designation systems (SKF, Schaeffler, NSK, NTN, JTEKT/Koyo, NACHI, Timken).

• SKF 6000–6400 deep groove ball bearing complete reference
• Deep groove ball bearing finder by bore, OD, width and seals
• Spherical roller bearing finder by bore and series
• Rolling bearing selection under ISO 15
• Bearing unit finder by shaft diameter (UCP, UCF, SY, FY, YAR)
• Bearing induction heaters and mounting tools

Questions on a marking, a suffix translation, a tier decision or how to build a register are welcome at sales@cballast.com. We answer whether or not you buy from us. Bearing specs and registers go to sales@cballast.com.

Compiled by cBallast for identification and cross-reference. Part numbers, designations and trademarks belong to their respective manufacturers. Confirm ratings and dimensions against the manufacturer's current documentation and the nameplate of the installed equipment before ordering or installation.