1-15/16" Bearing UCP210-31-Black Oxide Plated Insert + Pillow Block Housing Mounted BearingUCP210 31 Black Oxide Plated Insert Pillow Block Bearing Set Screw Type High Center Height 1 15 16" inch Inner Diameter UCP210 31Black Oxide Plated Insert Pillow Block Bearing, UCP210 31 is Set Screw Type High Center Height, Inner Diameter is 1 15 16". 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 31 Black Oxide Plated Insert