This is a plain back patio door roller assembly with a 1-1/4 in. concave or grooved steel ball bearing roller. It has a plain back housing that is 9/16 in. wide with a 13/16 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, Bennings, Scotty and a variety of other sliding patio door manufacturers.