These are mid-mount training wheels. Our training wheels do not bolt into the engine, which can cause major engine damage if the rider hits something! Wheel lock collars prevent from “sloppy” fitting wheels, which are unstable. Engineering: patent pending design. Safe, sturdy design. If we wouldn’t put these wheels on our children’s bikes, we wouldn’t sell them to you! Our design is tried n’ true! Wheels: Heavy duty wheels, tires and bearings – All-terrain tire tread style (wheel color and style may vary) Electro powder coat: Paint that is baked on at 400 degrees, and tough as nails! Assembly: Detailed mounting instructions with pictures, are included. These dirt bike training wheels are proudly made in the USA. At a small family business in Michigan. Please contact us with any questions. Or if you need to know if these will work on your model dirt bike. We would be happy to help. Please see our other listings for dirt bike training wheels that fit the following: Razor MX125 MX350 MX400 MX500 Honda CRF50 XR50 CRF50F Z50 Z50R Yamaha PW50 PW80 TTR50 Most 50cc , 70cc models including x pro 50cc dirt bike yamaha, plus many more styles.