Size--5''=12.7mm Diameter Grade Precision Balls. Material--Made Of Chrome Steel Which Has High Strength, Medium Corrosion Resistance, Good Hardness, And Wear Resistance. Package--100 PCS Chrome Steel Bearing Balls Precision Hardened Chromium Steel. High Quality--These Bearing Balls are Installed Between the Inner and Outer Rings to Reduce Friction During Bearing Rotation and Reduce the Ball Bearing Speed. Will Cause Less Damage to the Machine and Extend the Lifespan. Application--Bearing Steel Balls are Widely Used in High-Speed and Low-Noise Bearings, Bicycles, Motorcycles, Automobiles, Slides, Universal Balls, Bags, Casters, Drawer Slides, Door Locks, Electronic Industries, etc. 55