Pack of 10 1621-2RS Sealed Ball Bearings 1/2" x 1 3/8" x 7/16" inch 10 Ball Bearings Pack of 10 1621-2RS sealed radial deep groove ball bearings, 1621-2RS Bearings are made of Chrome Steel with chrome steel balls and steel cage, Bearings are closed with rubber seals to protect the Bearings from dust or any possible contamination, 1621-2RS Bearings are sealed and self lubricated, The quality is set to EMQ (electric motor quality) to ensure high speed, 1621-2RS Bearings are lubricated with grease.