The Polar FS1 Heart Rate Monitor Watch in dark blue is a versatile digital watch suitable for both indoor and outdoor activities. Powered by batteries, this heart rate monitor provides measurements in both decimal and imperial systems. Made of plastic, this wrist-worn watch features a variety of functions such as heart rate target zone, stopwatch, ECG heart rate, chronograph, and heart rate monitor. Designed for unisex adults, this Polar FS1 model is perfect for gym training and running, and it is compatible with Android operating systems.