S6203 Open Ball Bearing Premium ABEC-5 Quality with Si3N4 Ceramic Balls (Silicon Nitride) 17mm x 40mm x 12mm S6203 open stainless steel ball bearing, radial and deep groove ball bearing,S6203 bearing is made of Stainless Steel with Ceramic Balls (Si3N4) and Nylon Cage,the quality is set to EMQ (Premium ABEC-5 quality) to ensure high speed,inner diameter is 17mm, outer diameter is 40mm and width is 12mm.