Four row cylindrical roller bearings NTN is used almost exclusively for rolling mills. They have lower friction than other roller bearings and can be successfully used where high speed operation is called for. The low cross-sectional height of cylindrical roller bearings means that the roll necks can have a large diameter in relation to the roll itself.Depending on the application, four-row cylindrical roller bearings can be supplied with a cylindrical bore or a tapered bore. The inner and outer rings may be in one piece or in more than one piece.