For competitive riders looking to maximize every watt in training and racing scenarios, the Quarq Powermeter BB30 Elsa R Power Meter Crank Arms use SRAM's Exogram hollow carbon crank arms for uncompromising stiffness and power transfer. They're compatible with road bikes fitted with a BB30 bottom bracket interface and SRAM's 10 and 11 speed chainringsgroups both Yaw and non Yaw. The Elsa R measures power at the crankset spider with Quarq's OmniCal power measurement for greater precision. In fact, you'll find its spider fitted power meter delivers 1. 5% power accuracy readings, as well as power measurements along both the left and right cranks with its Power Balance Technology. This is crucial in evaluating weaknesses in both legs when you're looking to improve your training and racing times. Another benefit, as opposed to chainring dependent power meter cranks, is the ability to swap out chainrings to better suit your riding needs and local terrain. Communicating with ANT cycling computers, the Elsa R wirelessly transmits power and cadence data to popular cycling computers, such as Garmin's Edge 500, 510, 800, 810, 1000, and Forerunner 910XT models. It's also compatible with TrainingPeaks WKO, TrainingPeaks, Golden Cheetah, and Strava cycling apps. Furthermore, you'll find its replaceable CR2032 battery lasts some 300 hours of riding time, while its IPX 7 rating ensures protection from heavy showers and soaking road spray.