S609 Open Ball Bearing Premium ABEC-5 Quality with Si3N4 Ceramic Balls (Silicon Nitride) 9mm x 24mm x 7mm S609 Open Stainless Steel, radial and deep groove ball bearing,bearing is made of Stainless Steel with Ceramic Balls (Si3N4) and Stainless steel cage, the quality is set to EMQ (Premium ABEC-5 quality), inner diameter is 9mm, outer diameter is 24mm and width is 7mm.