This is an F-tab patio door roller assembly with a 1-1/4 in. concave steel 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 3/4 in. wide and 1-1/8 in. tall with a rear adjusting screw. Used by Christian Porter, Fullview and a variety of other patio door manufacturers.