S61905 Open Ball Bearing ABEC-7 Quality with Si3N4 Ceramic Balls (Silicon Nitride) 25mm x 42mm x 9mm S61905 Open Stainless Steel, radial, deep groove ball bearing,S61905 bearing is made of Stainless Steel with Ceramic Balls (Si3N4) and Nylon cage,the quality is set to EMQ (ABEC-7 quality) to ensure high speed,