7 x 17 x 5 Ball Bearing ABEC-5 Quality with Si3N4 Ceramic Balls Nylon Cage 7 x 17 x 5 Ball Bearing, double sealed, radial, deep groove ball bearings, bearing is made of Stainless Steel with Ceramic Balls (Si3N4) and Nylon cage, bearing is closed with rubber seals to protect the bearing from dust or any possible contamination, bearing is sealed and self lubricated, the quality is set to EMQ (ABEC-5 quality) to ensure high speeds, bearing is lubricated with Oil.