This is a bicycle U-lock bracket designed for heavy duty U-lock, its all-metal structure ensures durability, while with anti-slip shock absorber shim to prevent bumps and wobbles during driving, ensure that the bicycle U-lock will not fall off, improve your riding safety and convenience, providing a durable and stable locking effect. Fit For: 1.07-1.25 inch (27 mm to 32 mm) standard steel and aluminum bicycle frames, suitable for Kryptonite and most other brands of U-lock. Applicable frame: standard steel and aluminum bicycle frame 27 mm-32mm, Accommodates U-Lock shackles from (12mm-28mm).