61801-2RS Sealed Ceramic Ball Bearing ABEC-5 Quality with Si3N4 Ceramic Balls (Silicon Nitride) 12mm x 21mm x 5mm 61801-2RS Sealed Ceramic Ball Bearing is double sealed, radial and deep groove ball bearing,61801-2RS is made of Chrome Steel with Ceramic Balls (Si3N4) and Chrome steel cage,61801-2RS bearing is closed with rubber seals to protect the bearing from dust or any possible contamination,bearing is sealed and self lubricated,the quality is set to EMQ (ABEC-5 quality) to ensure high speed,61801-2RS bearing is lubricated with grease.