UCFX 4-Bolt Flange Bearing medium duty with two set screws and cast iron housing. This specific bearing has a wide inner ring with two set screws for the attachment to the shaft. As for the housing, it is a cast iron with a grease serk for re-lubricating the bearing. Keep in mind, that the medium bearings tend to have a larger housing and a larger OD bearing than the standard bearings. This specific design allows larger loads for the same sized shaft which makes it more efficient and convenient.