The WHOOP 4.0 (Brand New) with ONYX SUPERKNIT Strap is a premium fitness and health tracker designed for both indoor and outdoor activities. This activity tracker provides real-time data on heart rate variability, skin temperature, blood oxygen levels, and more. With a continuous battery life of days on a single charge, this tracker is perfect for gym training, weight lifting, yoga, and running. The sleek black design and compact size make it suitable for both men and women, and the water-resistant feature ensures durability during workouts. The WHOOP 4.0 is a top-of-the-line device from the trusted brand WHOOP, providing a full set of features for those looking to track their physiological data accurately.