SKF double row tapered roller bearings are ready-to-mount units, manufactured with a predetermined axial clearance or preload. TDO design bearings have a double-row outer ring and two single inner rings, usually with an intermediate ring between. Their roller sets are arranged back-to-back (O-arrangement), which enables them to accommodate tilting moments. Design variants include features such as a helical groove in the bore or lubrication grooves in the side faces of the bearing rings.