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. Ball material: carbon steel. Housing material: stainless steel. 750 pounds load capacity.