This is a 1-11/16 in. diameter by 7/16 in. wide concave or center grooved nylon steel ball bearing roller used on a variety of patio and wardrobe door roller assemblies. It has steel ball bearings and a standard 1/4 in. axle hole. Usually installed with a rivet into the inner roller housing. Replacement roller for Prime-Line part D 1555 used on Art Doors.