S6203ZZ Shielded Ball Bearing Premium ABEC-5 Quality with Si3N4 Ceramic Balls (Silicon Nitride) 17mm x 40mm x 12mm S6203ZZ is Double Metal Shields, radial, deep groove ball bearing,S6203ZZ bearing is made of Stainless Steel with Ceramic Balls (Si3N4) and Nylon Cage,S6203ZZ bearing is closed with 2 Metal Shields, one Shield from each side to protect the bearing from dust or any possible contamination,S6203ZZ bearing is sealed and self lubricated,the quality is set to EMQ (Premium ABEC-5 quality) to ensure high speed,S6203ZZ bearing is lubricated with grease.