1.Ball bearing.Roller bearing. hub bearing 2.Material,steel GCR - 15 3.Certificate: ISO 9001:2000 4.Hardness: 62 Deep groove ball bearings description:1. Material: Gcr15 Chrome steel, Stainless steel or Carbon steel2. Brand: TINMY3. High quality with very smooth feeling, quality standard: ISO9001:20084. Noise level: Z1,Z2,Z3,Z4; Vibration level: V1,V2,V3,V45. Innder windage code: C0,C2,C3,C4,C56. ...