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 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,IPX7 waterproof rating,Accuracy -- within 1.5%, measuring both legs.,.Specifications:Speeds: 11,Crank arm length: 170mm,BB Compatibility: All SRAM Road DUB BBs,Chainring Size: n/a,Bolt Circle Diameter (BCD): 110 BCD,Chainline: n/a,BB Spindle Interface: DUB,Chainring material: n/a,Guard: No Guard,Crank arm material: Carbon,Color (Crank arm): Natural carbon,Power Meter Type: Spider.