1/4" 5/16" 3/8 UNF SET SCREWS HEXAGON HEADS BOLTS A2 STAINLESS STEEL UNF BOLTS. 8.8 High Tensile Zinc Plated. Upgrade your projects with premium A2 Stainless Steel UNF Set Screws & Bolts! Available in 1/4", 5/16", and 3/8 sizes, these high-quality hexagon head bolts are perfect for industrial, automotive, and DIY applications. Built from corrosion-resistant A2 stainless steel, these UNF (Unified National Coarse) threaded bolts offer long-lasting durability and performance, even in harsh environments. The item must be unused and in its original packaging. We are here to help and will work to resolve any issues promptly. Please note that this service is available at an additional cost.