We'll tell you straight up that while we appreciate the appeal of Dura-Ace cassettes, we understand why you would choose Ultegra for your bike. Smart racers routinely save money by going with Ultegra cassettes; the money saved can go for other weight shaving measures. Shimano Ultegra CS-6700 Cassettes are lighter than their 6600 brothers, doing a nice job of closing the gap on Dura-Ace. The tallest cogs are riveted onto an aluminum carrier for weight savings, and they're more gentle on aluminum cassette bodies.