NTN Ultra- Class bearings are consistently manufactured to tight tolerances for concentricity and roundness. When combined with the high quality cage design and overall cleanliness these bearings provide greater accuracy of shaft rotation, quiet operation, longer bearing life and contribute to higher speed capability. Ultra Class inserts utilize a full contact molded rubber seal that is bonded to a steel backing plate. The metal flinger that protects the seal lip is pressed onto the inner ring. The ball point set screw is an NTN exclusive design. The setscrew absorbs vibration and is difficult to impossible to work itself loose. Heavy duty with solid base with a housing to outer ring fit which is held to tight tolerances. Also post the 2400 NTN bearings pdf.