NTN NU3 Series single row cylindrical roller bearing. NTN NU3 series cylindrical roller bearings have rollers that provide a modified line contact with the cylindrical inner and outer ring raceways, while the rollers are guided by ground ribs on either the inner or outer ring. The cylindrical shape allows the inner ring to have axial movement relative to the outer ring. This is especially important when accommodating thermal expansion, where both rings must be press-fitted.