The Polar Grit X is the perfect tool to take you through your toughest sessions and optimize your performance, taking your training to new heights. The ultra long battery life will not let you down, even in your toughest adventures, thanks to its military-standard durability. The Polar Grit X gives you hours of uninterrupted training with no compromise on weight, durability or design.Some of the many key features of the Grit X include; Real time route guidance from Komoot, Sleep quality tracking, Nightly Recharge™ recovery measurement ,Current Weather and Forecasts, Heart Rate monitor and the FitSpark™ training guide for tailored workouts, based on your recovery and readiness levels.The wristband comes in two sizes, so you can maximize comfort. The S/M comes in at 130-190mm and the M/L measures 145-215mm.