OTC 1908 6-pt. Locknut Socket (3-1/4”) - This high-grade truck wheel bearing locknut socket is made of high-strength steel with a 6 point opening 3-1/4". 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.