RMS8ZZ Sealed Ball Bearing 1" x 2 1/2" x 3/4" inch One Bearing RMS8ZZ Shielded Ball Bearing, RMS8ZZ is made of Chrome Steel with chrome steel balls and steel cage, bearing is closed with Metal Shields to protect the bearing from dust or any possible contamination, RMS8ZZ is Shielded and self lubricated,the quality is set to EMQ (electric motor quality) to ensure high speed,RMS8ZZ is lubricated with grease.