1/4"x11/16"x5/16" Sealed Ball Bearing is regular section, double Shielded, radial and deep groove ball bearing, bearing 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, bearing is Shielded and self lubricated,the quality is set to EMQ (electric motor quality) to ensure high speeds, bearing is lubricated with grease.