Function: Used to calibrate the tail hook of the bicycle frame to solve many transmission transmission transmission problems, especially in locating the rear transmission system. Product features: Aluminum alloy body, anodized Stainless steel measuring rod with clear scale 360 ° rotation correction, CNC turning and milling threads, tight fit. The aluminum alloy circular correction rod is made of aluminum alloy material, anodized, with enhanced hardness and reduced weight. Locking rotating rod, aluminum alloy anti slip detachable handle, precision thread, tightly fitting clockwise rotation positioning handle, screw in the bolt and change the lifting lug to lock. Sliding bracket, locking sliding bracket, can adjust the distance between the measuring rod and the wheel hub to measure the deviation between the tail hook and the wheel rim. 360° rotation correction, with the rotating rod as the axis and 360° rotation, measure the distance between the wheel rim and the tail hook to correct the tail hook. Stainless steel measuring rod positioning O-ring, made of stainless steel material, with clear scale and precise measurement. Move the measuring rod to contact the wheel, and then move the O-ring to align with the sliding bracket for positioning. Colour:Blue Material:Metal Package Contents: 1 x Bicycle Tail Hook Correction Tool Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is 1-3cm.