Steel with a zinc-yellow finish. 1 1/2" Nominal ID 3" outer diameter (OD) Thickness: 0.12'' Actual ID-1 5/8",Actual OD-3",Thickness-0.13"-0.2" 1 1/2" ID SAE high strength flat washers. Made of through-hardened steel with a zinc-yellow coating. These premium SAE flat washers are made of through-hardened high-strength steel and have a zinc-yellow chromate finish that provides superior corrosion and rust protection. SAE washers have a smaller ID and OD than their USS washer counterparts.