XX SL crank arm with an integrated power meter to record and deliver live, accurate power readings to your head unit- Spider design uses a proprietary chainring mount system which allows reduced weight without compromising reliability- Dual sided power measurement system calculates total watts, it's subtle, lightweight, and boasts unbeatable battery life- Compatible with the Flight Attendant system, allowing for total connectivity between all AXS enabled components- Choose 168mm or 174mm Q-factor (check frame manufacturer for specs)- BB and BB DUB spacers are not included