Developed with Quarq and bearing the S-Works badge of innovation and quality, Specialized's SpeedZone ANT+ Power Spider is set to take your metrics and performance to the next level. This strain gauge power meter is accurate to 0.5% and possesses a self-calibration mode at startup so your results stay accurate. The SpeedZone Power Spider is compatible with all ANT+ devices, so you can use the GPS unit or computer of your choice.