Train more effectively with the premium heart rate monitor. When worn around your chest during an activity, it wirelessly transmits your heart rate to your compatible device for instant feedback on how hard you"re working. The strap is made of a comfortable soft fabric. Adjust the size to your body for secure fit during your activities. Pair it with your ANT+ compatible device just once, and it will automatically recognize it each time. Optimized for use in crowded areas like the gym and road races, it won"t pick up any signals but your own. Taking care of it is a snap. The plastic heart-rate module is removable from the strap so you can wash the strap as often as needed. Doesn"t work with any Polar devices, which use a proprietary protocol. Battery is a standard 2032 Button and lasts for about a year with daily use.