Use Discount Strut Accessories 3/8" x 7/16" Stainless Steel Flat Square Washers to fit into slots or channels, prevent components from rotating, & distribute heavy loads. The 316 stainless steel material is ideal for outdoor use, has superior corrosion resistance, & is great for chemical or saltwater applications. Finish: ST316 Size: Bolt = 3/8"; Hole = 7/16"