Get more data out of your ride with the Quarq Elsa RS Power Meter Crank Arms. The Elsa RS pairs with a BB30 bottom bracket and Shimano Hollowglide chainrings for high performing, data gathering awesomeness. Five strain gauges in the spider work hard to capture every watt you put into the pedals with an industry leading 1. 5% accuracy so you can rest assured that all your post ride data file analysis doesn't go to waste. Quarq addresses the pesky occurrence of power meters needing to be recalibrating in changing weather and altitude with its Dynamic Temperature Compensation technology. No more stopping to recalibrate or freewheel during your rides. Just calibrate at the beginning of your ride and the Elsa RS takes care of the rest, letting you focus on that mountain pass PR without any worries about inaccurate data. The Elsa RS communicates with ANT head units to transfer power data and let you get the most out of your files, so chances are, it will pair with the one you already have. As an added bonus, Quarq's OmniCal power measurement technology lets you swap out chainring sizes without impacting the power reading accuracy.