Or you could save money. Break the chain, keep the links, loop the chain around the cog you want it on, ride as a ss, and then if you're on a super hilly road you have the option of throwing it back up on a lower ratio. Not as cool as a true conversion, but its more versatile. Best of all, it's sheldon approved. I saw the idea on his site a while back, but I can't yet figure out how to ctrl-c on my phone.