... carbon steel/stainless steel/mid-carbon steel surface:black/zinc 316 Stainless Steel Flat Washer Plain washer (or 'flat washer') is a flat annulus or ring, often of metal, used ... :Carbon steel, Stainless steel;Surface trearment: Plain, zinc plated etc.Standards:ISO,GB,DIN,JIS,ANSIISO/TS 16949,SGS,ROHS certificate. 316l Stainless Steel Flat Washer