The Halo series of bearings are a high quality steel/chrome bearing with rubber seals. These bearings have been tested and proven by many racers.
12x21x5 Halo bearing by Avid Racing Concepts is the standard outdrive bearing for nitro touring cars and 8th scale onroad cars such as the Kyosho RRR, Mugen MRX4, RPM Revo hub carriers, and Serpent 710. Check your manual for the correct size for your vehicle if you are not certain.