Polar h1 heart rate sensor comfort is the key when training thats why polar created the slim h1 heart rate sensor it not only measures your heart rate but also seamlessly adapts to your body shape so you can forget you are wearing it and focus on your exercise its even easier to put on than a pair of trainers soft textile material feels like clothing on the skin slim and streamlined connector design new improved user replaceable battery mechanism 5khz coded transmission compatible with m