A. The stem fixing screws of this mountain bike are made of metal, and the screw heads are made of titanium alloy. They are of good quality, sturdy and durable, providing reliable fixation for the bike. B. There are multiple specifications available, including two different lengths of M5x16mm and M5x18mm, to meet the needs of different users. Additionally, they feature a new top - hat head design, which is both stylish and practical. C. These screws are suitable for mountain bikes and are a good choice for fixing mountain bike stems. During cycling, they can effectively ensure the stability of the stem, enhancing the safety and stability of the ride. They perform well in both daily cycling and outdoor activities such as mountain biking. For bike enthusiasts, they are a great accessory. D. This product is widely sold in regions such as Europe, South America, Southeast Asia, North America, and Northeast Asia, and its quality has been recognized by many users.