.The specially hardened sockets with corrosion protection are designed for the removal of damaged , screws and nuts.The Twist socket design allows for a connection onto the rounded-off fastener to be extracted.The innovative spiral digs itself into the head of a damaged screw or nut, allowing it to be loosened.1/2 inch square drive for use with socket wrench or impact wrench. These broken bolt extractors have Black oxide surface provides greater strength and durability and prevents corrosion.Size:Driver size: 1/2 inchStraight bar diameter: 12mm/0.47 inchColor: black + red: plastic + metalPackage included:1* 17mm, 19mm, 21mm, 22mm ,26mm twist sockets1* 12mm straight rod and CaseOnly the above package content, other products are not included.Note: Light and different displays may cause the color of the item in the a little different from the real thing. The measurement allowed error is +/- 1-3cm.