S6801 Open Ball Bearing ABEC-5 Quality with Si3N4 Ceramic Balls (Silicon Nitride) 12mm x 21mm x 5mm S6801 Bearing is open, radial and deep groove ball bearing, the quality is set to EMQ (ABEC-5 quality) to ensure high speed, S6801 bearing is made of Stainless Steel with Ceramic Balls (Si3N4) and Stainless steel cage, bearings is lubricated with grease.