Garmin HRM-Tri Heart Rate Monitor COMPACT AND COMFORTABLE - HRM-Tri is the smallest and lightest heart rate monitor from Garmin. Designed with rounded edges and no exposed seams, the strap remains comfortable during extended hours of training. SWIM HEART RATE1 - Stores up to 20 hours of heart rate data during swims, then forwards it to a compatible device at the end of the session. It also sends real-time heart rate to the watch when the monitor is out of the water RUNNING DYNAMICS2 - Provides feedback on running form by measuring cadence, vertical oscillation and ground contact time when paired with a compatible device BATTERY LIFE - Lasts for 10 months (assuming 1 hour/day use) with user-replaceable CR2032 battery. Includes - HRM-Tri, manuals. Supports heart rate variability and advanced heart rate features