Hudson Bearings flange mounted ball transfer. 1-1/2-inches main ball rotates on ninety 3/16-inches support balls. Ball support cup is hardened and plated. Protective cover assures low torque and longevity. Neoprene cushion available to permit vertical deflection and assist with uniform load distribution. Carbon steel units are sealed and lubricated to ensure maximum life, unless otherwise specified. 250 pounds load capacity. Ball material: nylon. Housing material: carbon steel.