A. This carbon fiber stem spacer for the head tube of road bike forks is specially designed for people who pursue a better cycling experience. It comes in a variety of specifications with thicknesses of 3mm, 5mm, 10mm, 15mm, and 20mm respectively, and all have an inner diameter of 28.6mm. These options can meet different fitting needs. B. Made of carbon fiber material, this spacer ensures a certain quality, featuring high strength and good toughness. It can effectively reduce vibrations during cycling, provide stable support for the bike stem, and extend the service life of relevant bike components. Whether cycling on flat roads or rough mountain paths, it can fit your bike, making cycling smoother and safer. C. This product is popular in regions such as Europe, South America, Southeast Asia, North America, and Northeast Asia, and has won the recognition of many consumers with its reliable quality. D. If you want to improve the performance of your bike and the comfort of your cycling, this carbon fiber stem spacer is a good choice.