SMR74ZZ Sealed Ball Bearing 4mm x 7mm x 2.5mm SMR74ZZ metal shielded, radial and deep groove ball bearing, SMR74ZZ bearing is made of stainless Steel with stainless Steel balls and steel cage,SMR74ZZ bearing is closed with metal shields to protect the bearing from dust or any possible contamination,SMR74ZZ bearing is shielded and self lubricated,the quality is set to EMQ (electric motor quality) to ensure high speed,SMR74ZZ bearing is lubricated with grease.