The Hillman Group 2225 Number-4 Stainless Steel Flat Washer 50-Pack Flat washers are ideal for increasing the load bearing surface under a fastener's head by distributing the load through the washer These washers help to prevent bolts or nuts from pulling through a surface Stainless steels are used for their corrosion resistance, high-temperature strength, scaling resistance, and low-temperature toughness