This is a "F" tab patio door roller assembly with a 1-1/4 in. concave nylon ball bearing roller. 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 11/16 in. wide and 1-3/16 in. tall with a 7/8 in. dimple width. Used by Lupton and a variety of sliding patio door manufacturers.