S6900-2RS is double sealed, radial and deep groove ball bearings,S6900-2RS bearing is made of Stainless Steel with Ceramic Balls (Si3N4) and Stainless steel cage,S6900-2RS bearing is closed with rubber seals to protect the bearing from dust or any possible contamination,S6900-2RS bearing is sealed and self lubricated,the quality is set to EMQ (Premium ABEC-5 quality) to ensure high speed,S6900-2RS bearing is lubricated with grease.