Polar have pioneered the development of wireless technology and continue to further the technology in the field to improve resolution and eliminate interference. The WearLink+ transmitter W.I.N.D. is a result of that dedication. With a soft textile chest strap it’s the latest generation of Polar’s proprietary heart rate sensing and transmission technology. • Polar W.I.N.D. technology eliminates interference from external influences such as power lines Sizes: XS-S, M-XXL -Compatible with Polar RS800, CS600