【Applications】There are 6 sizes to choose from, which basically cover common frame head tube sizes. Please choose according to your specific needs.Black/Red Colors are optional, suitable for MTB, road bike, convenient and ble, easy to install,High-quality, low friction face-seals on the crown races.1-1/8" Threadle headset Completed with Headset expander plug,star nut and bolt.【Double-sealed bearings】Equped with double-sealed steel bearings to capture compreion rings and reduce the number of loose parts. It is smoother and easier to maintain than ball bearings, ing the handlebars light and smooth.【Easy to Install】Easy to install, save time and effort, good value for money. When driven, the bike feels as smooth as er.【Headset Expander Plug】Suitable for front fork with upper end outer diameter of 28.6mm, and carbon fiber front fork and mountain suspension fork are applicable.It can be used repeatedly, easy to install and disaemble, and can be installed in a few minutes with an a wrench. This proce eliminates the risk of damage and supports the fragile upper edge of the steering tube, which securely connects the front fork to the stem.