1,Long working life 2,Anti-rust and waterproof 3,Low price and good quality 4,The materials are bearing steel ... specialized dealing in Deep Groove Ball Bearings ,Spherical Roller Bearings, Tapered Roller Bearings, Automotive Bearings, Thrust Ball Bearings, and also dealing in household appliances , ... open bearing, Z, ZZ, RS, 2RS,RZ, OPEN4) Vibration and Noise level: Z1, Z2.5) Precition level: ABEC-1..6 ...