20mm Bearing UCF204 Black Oxide Plated Insert + Square Flanged Cast Housing Mounted BearingsUCF204 Black Oxide Plated Insert 20mm Mounted Bearing With Square Flanged Housing One Bearing UCF204 Black Oxide Plated Insert Mounted Bearing with square flanged Housing, the inner diameter is 20mm. Black oxide has certain properties and characteristics that makes it ideal for certain applications. It is used to add corrosion resistance and for appearance. Item: UCF204 Black Oxide Plated Insert Bearing Type: Mounted Bearing Bolt Size: M10 Shaft