VXB™ Brand, Polyurethane Rubber sealed wheel Ball Bearing with tire  6mm x 30mm x 12mm    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.  Item: PU 6x30x12 Ball Bearing  Type: Deep Groove Ball Bearing  Material: GCr15 bearing steel  Cover Material: Polyurethane(PU)  Seals: Rubber Seals  Size: 6mm x 30mm x 12mm  Bearing Inner Diameter: 6mm  Bearing Outer Diameter: 30mm  Bearing Width: 12mm  Quantity: One Bearing    6x30x12 Polyurethane RubberBearing 6x30x12 C3 Sealed Miniature PU0630-12-TIRE