The Evolution SuperTEK Hex Washered Head Screw, with a 16mm Bonded EPDM Washer, is designed for fixing steel to steel. Made from carbon steel with a AISI C1022 material grade with a 1000hr Evoshield coating. Single thread form ('V' fluted), drilling capacity of 3.5-18.5mm and a recommended drill speed of 1500-2500 RPM.