1638ZZ Shielded Ball Bearing 3/4" x 2" x 9/16" inch 1638ZZ Shielded Ball Bearing is radial, deep groove ball bearing,bearing is made of Chrome Steel with chrome steel balls and steel cage,1638ZZ 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 speed,1638ZZ bearing is lubricated with grease.