These bearing cover guide rollers feature a U-groove surface and a single bearing. They are optimal for medium load applications such as sliding doors or carrier transport. They are available in steel, hardended steel, plastic and stainless steel. These rollers can be used with RLR series rails (ordered separately). Hardened steel rollers are wear-resistant and prevent damage from intrusion of chips and other debris. Can be used with RLR rails. Body is made from nickel-plated 1045 steel, heat-treated 4135 steel with a black oxide finish, black plastic, or 303 stainless. Bearing and C-type retaining ring are made from steel or stainless.