... , Stainless steel or Carbon steel2. Brand: TINMY3. High quality with very smooth feeling, quality standard: ISO9001:20084. Noise level: Z1,Z2,Z3 ... 6200,6300,6400,51100,51200,51300,51400,DAC,BC, etc.Ring MaterialChrome Steel ,Carbon steel,Stainless steelTolerance gradeGB/T307.1- ... gland6.Noise inspection7.Appearance inspection8.Rust prevention9.Product packaging High quality deep groove ball bearings