UCP208-25 1 9/16" Black Oxide Plated Insert Pillow Block Mounted Bearing UnitUCP208 25 Black Oxide Plated Insert Pillow Block Bearing Cylindrical bore (with set screws) 1 9 16" 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.. UCP208 25 Black Oxide Plated Insert Bearing + Pillow Block Housing Mounted Ball Bearing Shaft Dia: 1 9 16" inch Bolt