Whoop 4.0 Health and Fitness Tracker Whoop measures sleep, recovery, strain, stress, etc and monitors health. 14+ day battery life. *Does require a membership; I believe $16 a month* The band is brand new, the device and charger are in used condition. Device and charger will be fully charged for you to set up and wear when you get it. I have 2 available for sale, please see my page. Will get it sent out same day - 1 day New to PoshMark? Sign up with referral code THEBUSYBEEE and earn $10 off your 1st purchase!