【 Function of Bearing 】Compared with other machinery, bearing is a small part, but it plays a pivotal role. It is mainly used to fix and reduce the load friction coefficient in the process of mechanical transmission. When other parts are moving relative to each other on the shaft, bearings can be used to reduce the coefficient of friction in the process of power transmission and keep the center of the shaft fixed.So as to increase the service life of the equipment 【Application】:These bearing are useful for bicycles, motorcycle,Skateboards, Longboards, Inline Skates, Electric Skateboards,toys， mower. 【High wear resistant material】: All the bearing are made of high quality chrome steel, high precision machine for accurate size. With lightly oiled on them to improve lubrication and protect against corrosion and rust. 【Well sealed】Rubber seal on both sides help to save grease and effectively protect grease from Impurities; Smooth rotation with low vibration, durable in use. 【Lifetime Guarantee】If you are not completely satisfied with this product, feel free to return the ammo with your proof of purchase and we will fully refund you.