This is an "F" tab patio door roller assembly with a 1-1/4 in. concave ball bearing roller that replaces the Old Style design. Used on Sun Valley, Fullview, Glasco and a variety of other sliding patio door manufacturers. When the corner screw passes through the "F" tab the assembly is captured by the side stile and bottom rail as the screw draws the two sides together. The housing is 9/16 in. wide and 1-9/32 in. tall, with a rear adjusting screw.