These are fully CNC machined from the highest quality 6AL4V aerospace grade Titanium and held to tight tolerances, producing a ROUND chainring. You know how much you hate tight/loose spots in your chain, right? This is the first step to eliminating that. They are fully reversible and symmetric so when one side wears out, just flip it over and you're good to go! Titanium already lasts forever, and this just doubles that.