I just bought myself a mountain bike at the flea market for $10 buckaroos. It needs some work done to it. It looks almost brandnew but the chain tension is missing which I don't know if I need or not. I was looking for a used mountain bike to buy and convert it to a single speed bike but don't really know how. I seen on the internet where they have conversion kits for sale and read a little bit on how to convert them. But I didn't see any pictures telling me what the heck a cassette is! My first thought was "Gee, I didn't know it came with a stereo!" Anywho, has anyone out there ever converted a multiple speed bike into a single speed? If so how is it done? And what the heck is a cassette?