This convenient socket is designed to fit a 1-3/4" castled (or castellated) wheel axle nut used on a 1-1/2" dia. aviation aircraft axle. With a 3/8" drive ratchet engaged in the socked and the socket engaged in the castellated nut, the aircraft wheel can be easily removed or installed and tightened to the desired torque. It's especially useful where a regular socket won't fit.