This is a plain back patio door roller assembly with a 1-1/4 in. concave steel ball bearing roller. It has a plain back housing that is 3/4 in. wide with a 7/8 in. flare and 1-3/16 in. tall. It is rear adjusting with a threaded mounting hole on the back end. It is used by Nu-Air and a variety of sliding patio door manufacturers.