Reach new goals and explore new roads with a power meter that delivers on accuracy, durability, and reliability. The Quarq DFour DUB Power Meter is paired with the Quarq DUB Crankarms to pair with your Dura-Ace R9100 or Ultegra R8000 chainrings. A SRAM DUB Bottom Bracket will be required for installation.Key Features:Bluetooth low energy technology and ANT+ wireless data transferMagicZero - automatically checks and recalibrates your power meter as you rideno need to manually calibrateAxCad -- no cadence magnet required10K Temperature CompensationBattery -- CR2032, 200-hour battery life, change without toolsOmniCal -- swap chainrings without affecting accuracyIPX7 waterproof ratingAccuracy -- within 1.5%, measuring both legs.Specifications:Speeds: 11Crank arm length: 170mmBB Compatibility: All SRAM Road DUB BBsChainring Size: n/aBolt Circle Diameter (BCD): 110 BCDChainline: n/aBB Spindle Interface: DUBChainring material: n/aGuard: No GuardCrank arm material: CarbonColor (Crank arm):