This blued steel sling swivel screw, is made to accept a 3.0mm swivel pin and to go on 6mm wide swivel heads. The M5 thread means you fix the screw to you forearm or stock using a nut and washer rather than screw directly into the wood.
Thread of Screw - M5 Hole Diameter - 3.0mm or 3.6mm Head Width - 6mm or 8mm Thread Length - 22mm Total Length - 30mm Code Ref: 3.0mm - 20230-0022 3.6mm - 20240-0022
