SR156ZZ is regular section , metal shielded, radial and deep groove ball bearing, bearing is made of stainless Steel with Silicon Nitride Ceramic balls and steel cage, bearing is closed with metal shields to protect the bearing from dust or any possible contamination, SR156ZZ bearing is shielded and self lubricated,the quality is set to EMQ (electric motor quality) to ensure high speed, bearing is lubricated with grease.