This is a "E" tab patio door roller assembly with a 1-1/2 in. concave nylon ball bearing roller in a stamped steel "E" tab style housing. As the corner screw passes through the "E" tab it captures the roller assembly and positions it in the door's bottom rail. The housing is 5/8 in. wide and 1-7/16 in. tall with a rear adjusting screw. Used by Marshall and a variety of other sliding patio door manufacturers.