Hudson Bearings Drop-In heavy duty ball transfer. Metal cap for additional strength and durability. Integral flange at top allows unit to be dropped into 1-3/4-inches diameter hole. 1-3/16-inches main ball rotates on 1/8-inches support balls. Ball support cup is machined from solid steel and is hardened and plated. Retaining ring is solid metal. Carbon steel units are sealed and lubricated to ensure maximum life, unless otherwise specified. Ball material: carbon steel. Housing material: carbon steel. 750 pounds load capacity.