18-8 / 304 Grade Stainless Steel Standard Flat Washers. These are Standard Commercial Pattern Flat Washers in Stainless Steel. Plain Washers are Commonly Used With a Varity of Fasteners Including Bolts, Screws, and Nuts. Made of 18-8 / 304 Grade Stainless Steel. These are the Most Popular Variety of a Flat Washer for Many Production Applications.