This is to be used with a breaker bar to loosen stubborn oxygen sensors. Tool comes with both 0.5in and 0.375in drive. Attach a 0.5in breaker bar on the end of the tool to initially loosen stuck sensors. Use a 0.375in ratchet on the top for fast removal and installation. Fits oxygen sensor applications with a heat shield. Slotted body allows clearance for wire harnesses. Forged heat-treated steel with six point design will withstand high torque removal applications.