High quality CNC machined hollow lever This quick-release seat post clamp is extremely strong and lightweight. You can install them easily on your bike, even if you are not professional in repairing bikes. Designed to achieve an efficient clamping effect even in wet and mud without slipping. Hollow lever design and rust resistant, high quality thumb screw for accuracy and a quick release lever for easy handling. The surface is smooth and bright after anodized mechanical grinding without edges and corners. Caliber is 31.8mm, 34.9mm, 31.8mm seat post clamp is generally suitable for 27.2mm seat post, 34.9mm seat post clamp is generally suitable for 30.8mm-31.6mm. Easy to install and use. The diameter of the required clamp is the frame, not the diameter of the seat post. It is ideal for all types of bicycles that require a seat post.