Sends accurate real-time heart rate and HRV data to compatible Garmin smartwatches and cycling computers, fitness equipment, and apps Comfortable machine-washable strap is available in two sizes (XS - S and M–XL) for the most ideal fit for your body type Understand how much you slow down when your foot hits the ground with step speed loss, and improve your running form with additional running dynamics, including stride length, vertical oscillation and ground contact time balance (requires compatible smartwatch) During activities where you can’t wear a watch, such as team sports, HRM 600 will record the workout and sync data, including heart rate, calories, speed, distance and more, directly to the Garmin Connect smartphone app Tracks daily metrics, including estimated steps, heart rate, calories burned and more, and syncs that data directly to the Garmin Connect smartphone app For indoor track and treadmill runs, HRM 600 sends pace and distance to your compatible smartwatch Provides and stores accurate heart rate data during swim activities and syncs it to your compatible smartwatch after you save your workout Up to 2 months of battery life with a rechargeable battery XS-S: Fits chest circumferences 60-85cm (23.5" - 33.5") M-XL: Fits chest circumferences 80-119cm (31.5" - 47")