ISO 8738 round flat washer, 18 x 28 x 4 mm, Article number 8738A418. Made in stainless steel a4. Round Flat Washer manufactured to ISO 8738. Standard parts to the same standard, property class, dimensions and surface finish are interchangeable between manufacturers; confirm the controlling standard revision, any class-society or application approval, and the mating thread before substitution. Applications: load distribution and locking under bolt heads and nuts in machine building, structural steel, plant maintenance and marine outfitting.