This is a Plain Back patio door roller assembly with a 1-1/2 in. concave or grooved steel ball bearing roller. It has a plain back housing that is 3/4 in. wide and 1-3/8 in. tall. It is rear adjusting with a 1/4-20 threaded mounting hole on the back end and an optional use 10-32 threaded hole on top. It is used by Air Control, Howmet, Krestmark and a variety of other manufacturers of patio doors.