Every innovation in Quarq’s next-generation DZero platform is channeled into DFour. It embodies 10 years of Quarq technology advances with new features such as dual Bluetooth low energy and ANT+ wireless data transfer, the new Qalvin BLE app and compatibility with BB386EVO bottom brackets.Designed for Dura-Ace 9000 chainrings. Compatible with Ultegra 6800 and 105 5800 chainrings..Must be paired with a compatible SRAM bottom bracket..ELSA RS power meter owners can upgrade using the DFour Power Meter Spider..Free firmware upgrades with the Qalvin app..BB30 versions ship with the spacers and wave washer required for BB386EVO installation..Key Features:Bluetooth low energy technology and ANT+ wireless data transfer..AxCad - no magnet..10K Temperature Compensation..Battery - CR2032, 200-hour battery life, change without tools..OmniCal - swap chainrings without affecting accuracy..2-year warranty..IPX7 waterproof rating..Accuracy - within 1.5%, measuring both legs..Specifications:Material - CNC Machined Aluminum Spider, Exogram™ Carbon Crank Arms.Accuracy - 1.5%.Bolt Circle Diameter - 110 Asymmetric BCD.Arm Lengths - 162.5mm, 165mm, 170mm, 172.5mm, 175mm, 177.5mm.Q-Factor - 145mm.Bottom Bracket - GXP, Press Fit GXP, BB30, Press Fit 30, BBright, BB386EVO, BB30A, PF30A.Wireless Technology - ANT+, Bluetooth low energy technology.Battery - CR2032, 200 hours of riding time.Weight - 588g.Head Unit - ANT+™ and Bluetooth® low energy technology compatible head units (available separately).Analysis Software - TrainingPeaks WKO4®, TrainingPeaks®, Today's Plan, Golden Cheetah, Strava® and others (available separately).Compatibility - Shimano® 11-speed chainrings (except for R9100). Designed for Dura-Ace® 9000. Compatible with Ultegra® 6800 and 105® 5800..