I bought a few different sizes to try them out, and the quality of the cog is great. They are lightweight, great quality Aluminum and top notch machining. I've put a ton of miles on them and they are wearing very well. Also they have a taper so the portion that rests on the freehub is wider, and thus more stable. Cheap cogs will cut into your hub. Don't make that mistake, get a Kick Ass Cog!!!