OTC 1951M Metric Truck Wheel Bearing Locknut Socket 55 mm (6-pt) - Specially designed socket easily removes or installs locknuts. Made of high strength steel and resist rounding out. Measure from flat to flat to determine size of locknut, then consult chart below to find the correct socket. NOTE: Sockets are designed for use with 3/4" square-drive manual tools only. Impact tool use VOIDS sockets' warranty.