Accurate power measurement is key to success. The Sram Red Quarq Power Meter is built into the crank itself to offer excellent accuracy of +/-1.5% combined with a low weight & clean look. Just like the standard Red crankset, this Quarq Power Meter version is built to the very best standards, with Exogram hollow fibre cranks & compatible chainrings which line up the derailment pins behind the crank for a clean look. IPX7 waterproofing, a 2 year warranty, & worldwide support ensures the Red Quarq Crankset will outlive your current bike. Ax Cad Accelerometer Cadence turns the power meter on when it senses motion & also measure your cadence, making the Red Quarq Power Meter simple to use. IPX 7 Waterproof Rating & 2 Year Warranty Ensure Maximum Reliability in all Weathers Compatible with Sram 11 Speed Groupsets & Sram Red Yaw 10 Speed Exogram Hollow Crank Arms Minimise Weight yet Maximise Speed Description by Mark, Rutland Cycling Web Team.