Manufacturer: Whoop Model: WS40 Description: 4.0 Fitness Tracker Superknit Onyx Product has been used, I no longer use it. It's in prefect working condition Color: Onyx. Superknit Band. Bluetooth. Tracks: Average Heart Rate, Sleep, Calorie Monitor & Data Review. Waterproof To 10 Meters. Compatible With: iOS & Android. ***THIS ITEM REQUIRES A SUBSCRIPTION/MEMBERSHIP FROM THE MANUFACTURER TO FUNCTION - AND IT IS NOT INCLUDED*** Includes the Whoop 4.0 tracker, two bands and two chargers.