DIN 9021 round flat washer, 10.5 x 30 x 2.5 mm, Article number 9021B105. Surface finish: plain. Round Flat Washer manufactured to DIN 9021. 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.