Bicycle Bearings are used to reduce friction between two surfaces. You can find bearings in the front or rear hub in your wheels, inside the bottom bracket where the axle is connected to the cranks and in the frame where your headset sits. Bicycle Bearings apply to either mountain bikes or road bikes. These can also be used in chemicals, aerospace, plastic hardware, etc. High-quality 304 material, resistant to acid, alkali and corrosion, not easy to rust.