Polar H1 Heart Rate SensorTrack your heart rate and perform at your best with the Polar H1 Heart Rate Sensor. Not only does it measure your heart rate, it also seamlessly adapts to your body shape so you can focus on your exercise. Soft textile material has a cloth-like feel to ensure comfort. Slim design. New improved user-replaceable battery mechanism. 5kHz coded transmission, compatible with most Polar products and compatible gym equipment in fitness clubs.