I purchased a thumb assist to install on my ATV or 4-wheeler generally known as a thumb saver which is supposed to reduce fatigue when the vehicle is used for extended periods of time. I installed it per instructions and it worked freely and everything appeared to be in order. Later when we went riding our 4-wheelers I went to turn around in a trail that was on a grade parallel to the vehicle which required me to stand up to retain my balance. When I did this my leg engaged the throttle because th thumb assist sticks out way beyond the position of the stock throttle lever. The result was that the 4-wheeler lurched forward into a tree which threw me into the throttle again. The 4-wheeler proceeded to climb up the tree until it turned over backwards on me resulting in a severe tear to my right shoulder rotator cuff. I have looked at what the situation would be with applications on all different manufactures of 4-wheelers and the results were always the same, CATASTRAFIC! this is a terrible design an should be outlawed. any one who has experienced the same fate can reach me at [email protected]. Thanks, Disabled & Broke