The revolutionary machined design of the Sram XX 10 Speed Cassette uses the same gruelling 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. The process takes 9 hours per cassette! You have never seen a cassette that looks like this. The open design aids in mud clearance, giving you cleaner shifting performance and longer component life.