The revolutionary machined design of the XX Cassette uses the same grueling manufacturing techniques that produced the PowerDome road cassette. With X Dome, eight of the cogs are CNC machined together out of a single block of billet steel, creating an incredibly lightweight, precise and strong cassette. Its a process that takes nine hours per cassette! You have never seen a cassette that looks like this. The open design aids in mud clearance, giving you cleaner shifting per formance and longer component life.