This is an F-tab patio door roller assembly with a 1-1/4 in. concave or grooved 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 9/16 in. wide, 1-3/32 in. tall with a rear adjusting screw. Used by Superlite, Fenton and a variety of other sliding patio door manufacturers.