Opening size is 6 point and 3-1/2 inchesSpecially designed and makes wheel bearing locknuts easy to remove or installMade of high-strength steelResists rounding outSocket is designed for use with 3/4 inch square-drive manual tools only; Impact tool use voids socket warrantyThe OTC 1910 is specially designed and makes wheel bearing locknuts easy to remove or install. It's made of high-strength steel and resists rounding out. Opening size is 6 point and 3-1/2”. NOTE: Socket is designed for use with 3/4” square-drive manual tools only. Impact tool use voids socket warranty.