6308‑2Z/C3 Deep Groove Ball Bearing 40x90x23mm for Conveyor and General Industrial Equipment Product Overview 63 series 2Z/C3 are single row deep groove ball bearings fitted with double metal shields and C3 enlarged clearance. Factory pre‑greased for dust‑proof and high‑speed operation. C3 clearance accommodates shaft thermal expansion under high‑temperature working conditions. Made of standard bearing steel, good interchangeability for general industrial rotating equipment.