Cylindrical roller bearing are classified by the rib types. The outer ring of a NU-type bearing has two ribs and the inner ring has no rib.The inner ring of a N-type bearing has two ribs and the outer ring has no rib.     NU-type and N-type cylindrical roller bearings are used at a floating end.As separable bearings, they are easy to assembly and dismantle,with tight fit suitable for both inner ring and outer ring.     The outer ring of a NJ-type cylindrical roller bearing has two ribs and the inner ring has one,being able to endure the axial force in one direction。     Cylindrical roller bearing has a large radial bearing capacity for all kinds of hot and cold rolling mills with frequent roll replacement, so it is suitable for the work roll or support roll on all kinds of hot and cold rolling mills, billet mills and other rolling mills.