Smart watch + GPS that puts motivation on the wrist. Motivation, inspiration, personalization: Built-in GPS – leave your phone at home and track pace and distance during runs, rides and more with built-in GPS, then view a map of exercise intensity in the Fitbit app; 24/7 Heart Rate – maximize exercise with heart rate zones, track sleep stages and better estimate calorie burn with PurePulse 2.0, Fitbit’s enhanced heart rate technology.; Active Zones in Minutes – uses your resting heart rate to measure exercise effort and gives you a sound when you increase the intensity to get the most out of your workout; Sleep Tracking and Sleep Scores – Track your time in light, deep, and REM sleep, then receive a sleep score to better understand your sleep quality each night. Battery life 6+ days with fast charging. S and L size belts included.