DIN 125-B round flat washer (form B), 31 x 56 x 4 mm, Article number 125BR310. Surface finish: plain. Round Flat Washer manufactured to DIN 125. 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.