Material: spring steel ,stainless steel,carbon steel,etc Surface: Zinc plated or Black Size: M6-M100(1/4-4inch) Features: 1.Flat washer and Spring washer Monel 400 K500 2.Standard: GB, ISO, DIN, BS, ANSI/ASME, JIS 3,Size: M6-M100(1/4-4inch), also according to customers' reqquirements. 4.Material: super duplex stainless steel, incoloy, incolonel, hastelloy, monel, nimonic etc. 5. Grade: 4-10, A2, ...