I bought my bike used, and the guy who had it before me must think he has to tighten everything as TIGHT AS HUMANLY POSSIBLE! Every single bolt and screw has been tightened so much that its almost impossible to remove. And now I just rounded off the head of one of the sprocket bolts. They are hex heads and I was using the exact size tool, which shows how much force I had to use to actually strip one of those things. Even the little screws on the plastic chain guard were tightened to the max. Guess what, stripped those too. So I grabbed a crobar and broke that little plastic ****er off. Now I have to figure out what I'm gonna do about that bolt. FAWK!!!