1-1/2" Bearing UCF208-24 Black Oxide Plated Insert Bearing + Square Flanged Housing Mounted BearingUCF208 24 Black Oxide Plated Insert + Square Flanged Mounted Bearing 1 1 2" inch Inner Diameter UCF208 24 Black Oxide Plated Insert Bearing + Square Flanged Housing Mounted Bearing, Inner Diameter is 1 1 2" inch. Black oxide has certain properties and characteristics that makes it ideal for certain applications. It is used to add corrosion resistance and for appearance. UCF208 24 Black Oxide Plated Insert Bearing + Square Flanged Housing Mounted