Calibrated Z1 Fluid head accurately measures your training session. Monitor current, average, and maximums for power, heart rate, and speed. Training zone control alerts you when outside preset heart rate zones. HYDROGEL roller reduces noise by 55% and tire wear by 25 30%. Progressive resistance up to 900 watts. SRS Smart Release System makes mounting quick and easy. Wireless backlit display, heart rate transmitter, and coaching CD included. Lifetime warranty. Fits 26, 700c, and 29 wheels. Adapter available for 24.