Check the listing for details. Precision Balls 12mm Solid Chrome Steel G10 for Bearing Keychain Wheel 10pcs. Condition: New. Listed at 10.82 USD. Descriptions:1. These high precision chrome steel balls are hot forged from bar stock.2. Modern furnaces with precisely controlled atmospheres and temperatures are used for heat treating to assure uniform hardness and proper microstructure for each steel ball.3. Ball hardness is controlled within the 60-63 HRC range as measured on parallel flat surfaces.4. Bearing balls are used for semi-precision bearings, and in commercial applications such as casters, locks, and drawer slides.5. Other applications for steel bearing balls include drawer slides, door locks.Notice: Watch out for rust, store in a dry place. Conditions such as high humidity or prolonged time outdoors can cause rusting.Specifications:Size: 12mmPrecision Grade: G10Hardness: 60-63Material: High Carbon Chromium Bearing Steel (GCr15)Package Contents:10 Pack x Bearing Ball.