Hudson Bearings flange mounted ball transfer. 1-inches main ball rotates on eighty 1/8-inches support balls. Ball support cup is hardened and plated. Protective cover assures low torque and longevity. Nylon main ball for non-marking applications. Carbon steel units are sealed and lubricated to ensure maximum life, unless otherwise specified. 35 pounds load capacity. Ball material: nylon. Housing material: carbon steel. Nylon main balls are machined, hardened, and non-marring.