UCF205-15 Black Oxide Plated Insert + Flange 4-Bolt 15/16" Bore Mounted BearingUCF205 15 Black Oxide Plated Insert + Flange Units 4 Bolt Set Screw Locking 15 16" Inner Diameter Ball Bearing UCF205 15 Black Oxide Plated Insert + Flange Units 4 Bolt Ball Bearing, UCF205 15 is Set Screw Locking, bearing has solid base housing construction, bearing has wide inner ring. Black oxide has certain properties and characteristics that makes it ideal for certain applications. It is used to add corrosion resistance and for appearance. UCF205