Looking to stay warm during your outdoor activity? The women’s Fieldsheer powered by Mobile Warming Technology Bluetooth®-enabled Ion heated baselayer shirt offers light-weight performance and an integrated Far-Infrared heating system. The Ion is a next-generation baselayer that delivers 7.4-volts of instant heat for hours through our exclusive Bluetooth®-enabled integrated touch control button. Use the free MW Connect™ app to adjust temperature or check battery levels. Choose from 4 heat settings to keep you warm and comfortable for hours. From skiing and hiking to running or just spending time outdoors, the Ion Shirt compliments your outerwear to keep you warm and comfortable.