Polar has revealed its new Grit X will test the limits of the most ardent ultra runners with a battery life that’ll last for 40-hours, even with all of the keys features turned on.

The brand new multi-sport Grit X watch brings built-in GPS, heart-rate tracking, barometer, compass and an altimeter, as well as all of the Polar Flow smart couching tools, can all be enabled without risk of the battery conking out within hours.
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