A. This is a bottom bracket fixing screw suitable for mountain bikes and 412 folding bikes. The screw is made of metal, specifically titanium alloy. This material can ensure that the screw has good quality and durability, and can withstand relatively large pressure and friction. It is not easily damaged even after long - term use. B. Its specification is square hole M8x15mm. The precise size design allows it to fit the corresponding bicycle models well, and the installation process is easy and convenient. In addition, this screw has a waterproof function, which can effectively prevent moisture from intruding, avoid performance degradation and shortened service life caused by rust and corrosion, and ensure the stable operation of the bicycle bottom bracket. C. Whether you are facing complex and changeable road conditions during mountain cycling or performing frequent folding operations in the daily use of a folding bike, this screw can play an important role, providing reliable support for your cycling and making you feel more at ease when riding. D. It is suitable for multiple sales regions, such as Africa, Europe, South America, Southeast Asia, North America, Northeast Asia, and the Middle East, and can show good performance in different environments. In addition, it has an authorized own brand, and its quality is trustworthy.