These rollers are constructed of steel components and include a set of installation nuts and bolts for each. Each wheel has a concaved (center grooved) edge and features a steel inner race, steel ball bearings and a 1/4 in. inside diameter hole. The outside diameter of these rollers measures 1-1/4 in. and the width (or thickness) is 5/16 in.. These wheels are commonly used to repair damaged sliding patio door roller assemblies in both the glass and screen sliding door panels. These wheels are used by a variety of patio door manufacturers.