Quarq DFour AXS DUB Power Meter Spider combines the advanced power meter technology with SRAM's innovative DUB platform to bring you a simple spider-based power meter. Features: Simplified part choices, quality materials and a broader compatibility for bottom brackets and chainrings, brings power on every ride DFour DUB is designed for Dura-Ace R9100 chainrings Spider must be paired with a compatible Quarq DZero DUB crankset and SRAM DUB bottom bracket Bluetooth low energy technology and ANT+ wireless data transfer MagicZero technology automatically checks and recalibrates your power meter as you ride - no need to manually calibrate AxCad system provides no-magnet cadence data Use the AXS app to easily update firmware and view power meter metrics Measures power for both legs with +/- 1.5% accuracy Uses a CR2032 battery that can be replaced without tools OmniCal system allows you to swap chainrings without affecting accuracy IPX7 waterproof rating Specs: Chainring BCD 110mm Color Black