FEATURE SOLID QUANLITY -Compare to the normal thread,the tool use the ACME thread rod,stronger and not easy to move. -The wide hook and bolts made from 40cr steel,more durable and longer service life. LOCKS INTO PLACE -Acme threaded rod built-in detent pins to lock the coil spring in place for safer spring compression. EASY STORAGE – Professional Package for easy transportation and safe storage. NOTES 1.Recommend to use with a 21mm (13/16″) hexagon socket wrench or 1/2″ square drive ratchet wrench. .