I got a Livefast 40t to replace the stock one on my BoyGoFast kit, and they're the bee's knees! It has just enough speed to get me to a comfortable cruising speed, where the stock 50t would have the engine revving worrisomely. I don't think it quite gets to thirty, but it's fast enough that I don't go WOT all the time. I got it from their ebay store, where it is bundled with a new chain and U-style motor mounting bracket, which will be handy for spare parts, say if I lose a masterlink, all for $28 shipped. A single 36t cost more than that! It's good deal, I'd say.