Spline / Triple square Impact Sockets 3/8" And 1/2" Drive Manufactured from chrome vanadium steel and hardened for strength and durability. Triple square / spline / 12 sided sockets this limits the amount of wear on the corners of the fastener and the socket as you have more sides / teeth on the socket biting onto the item. SET Includes; SIZES : M6 (total length 50mm) 3/8" drive M8 (total length 58mm) 3/8" drive M10 (total length 67.8mm) 3/8" drive M12 (total length 108mm) 1/2" drive M14 (total length 108mm) 1/2" drive M16H (total length 108mm) 1/2" drive tamperproof (hole for security bits)