If you're here, then you know. Shimano's XTR M9000 Race Brakes are some of the best brakes we've encountered, and we'd love for them to be on all of our bikes. The combination of low weight, consistent lever feel, and unadulterated braking power makes them sought after by XC racers, weekend warriors, and bike geeks alike. They're also compatible with the latest generation of Shimano's I Spec design, I Spec II. If you've got a pair of I Spec II shift levers, you can save valuable cockpit real estate by attaching both the shift and brake levers with one clamp. At first glance, they don't appear that different from the previous generation, but you can't judge a book by its cover. The caliper and master cylinder are now magnesium, and the levers are carbon fiber. Shimano dumped its Servo Wave cam in favor of a redesigned lever path that provides a smoother transition between off and on the brakes, and a more progressive feel throughout the braking process. Shimano's also made a number of small improvements to manage heat buildup better, but recommends the new Freeza rotors for maximum performance with these brakes.