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. Features: Bluetooth low energy technology and ANT+ wireless data transfer MagicZero - automatically checks and recalibrates your power meter as you ride – no need to manually calibrate AxCad -- no cadence magnet required 10K Temperature CompensationBattery -- 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.