S6905 Open Ball Bearing ABEC-7 Quality with Si3N4 Ceramic Balls (Silicon Nitride) 25 x 42 x 9 mm S6905 Open Stainless Steel, radial and deep groove ball bearing,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,inner diameter is 25mm, outer diameter is 42mm and width is 9mm