8x45x14mm Polyurethane Rubber roller wheel Bearing Sealed Miniature - tirePolyurethane Rubber sealed Wheel Ball Bearing with tire 8mm x 45mm x 14mm Polyurethane ( PU) is a new type of polymer composite materials between rubber and plastic, offering higher load bearing capacity compared to plastic, polyurethane offer superior impact resistance, while good mechanical properties. Polyurethane have better abrasion and tear resistance than rubber. PU 8x45x14 Ball Bearing Deep Groove Ball Bearing Material: GCr15 bearing steel