The Fitbit Alta FB406BKL-EU fitness activity tracker in size Large and color Black is a versatile device designed for both indoor and outdoor activities. With a battery life of up to 5 days, this activity tracker provides accurate measurements for heart rate, speed, cadence, time, calories, and distance. It features a variety of functions including GPS, smartphone compatibility, set goals, and sleep tracking. Made of steel, the device is compatible with Windows, iOS, and Android operating systems, making it suitable for unisex adults engaged in activities such as gym training, weightlifting, yoga, and running.