This is an Unique Back diecast patio door roller assembly with a 1-1/4 inch concave steel ball bearing roller used on Crossly doors. It's unique diecast housing is 11/16 inches stepping down to 9/16 inches wide, 1-1/8 inches tall and 2-5/16 inches long with a flare width of 3/4 inches. The 9/16 inch wide rear design of the housing fits into the door rail held in place by a screw that engages the mounting hole in the back end. The adjustment screw is just above the mounting hole.