Fitbit Charge 4 - Health and Fitness Tracker (Brand New)Brand New Sealed in Box Universal one size 2 Year Warranty The water resistant Fitbit Charge 4 has been created with a battery that will provide up to 7 days usage, a POLED screen, built in GPS, sleep tracking and heart rate monitoring. This stylish device provides convenience on the go and can help to inspire you to hit your health and fitness goals. Active Zone Minutes Fitbit has created a new metric: Active Zone Minutes (AZM) to help you work out