These VANSIHO bike headset bearings are made of high-quality steel, which has excellent wear resistance and is not easy to rust. The bearing surface is processed by black oxide, which has good anti-corrosion and wear resistance. The bearing has a built-in steel cage, which can effectively prevent the bearing from falling off and ensure the smooth operation of the bearing. The bearing has a small inner diameter and a large outer diameter, which can accommodate various types of bicycles and is suitable for most mountain bikes, road bikes, and BMX bikes. The bearing is easy to install and requires no tools. It is a great replacement for your old or damaged headset bearings.