S61802 Open Ball Bearing Premium ABEC-5 Quality with Si3N4 Ceramic Balls (Silicon Nitride) 15mm x 24mm x 5mm S61802 Bearing is open, radial and deep groove ball bearing,the quality is set to EMQ (Premium ABEC-5 quality) to ensure high speed,S61802 bearing is made of Stainless Steel with Ceramic Balls (Si3N4) and Stainless steel cage, bearings is lubricated with grease.