The quartz sleeve separates the ultraviolet lamp from the water while passing UV-C into it. Length and diameter both identify a sleeve, and this catalogue stocks several at similar lengths — order against the reactor model rather than against a measurement of the old part alone. Note that this catalogue also lists a 909 mm quartz MODULE for the SLR2581 under item 1379-0108 — the module is the complete assembly, this row is the bare sleeve. Wedeco was founded in Herford, Germany in 1976 and is now a Xylem brand.