UCP210-30 1-7/8" Black Oxide Plated Insert Pillow Block Mounted BearingUCP210 30 Black Oxide Plated Insert Pillow Block Bearing 1 7 8" Inner Diameter Bearing This is the most common type of mounted ball unit. Black oxide has certain properties and characteristics that makes it ideal for certain applications. It is used to add corrosion resistance and for appearance. UCP210 30 Black Oxide Plated Insert Bearing + Pillow block Housing Black Oxide Plated Insert Mounted Ball Bearing Shaft Dia: 1 7 8" inch Bolt Size: 5 8" inch