The women’s Fieldsheer powered by Mobile Warming Technology Bluetooth®-enabled Ion women's heated baselayer shirt is designed for the outdoor enthusiast. From skiing, hunting, and hiking to running or just spending time outdoors, the Ion shirt complements your outerwear to keep a warm core. Its moisture-wicking, warmth, and stretch features make it a versatile baselayer in the winter, or a standalone shirt during outdoor activity in the Spring and Fall. The Primer is made from a four-way stretch anti-odor polyester-spandex blend that provides a comfortable next-to-skin feel. Flat-lock seams, moisture-wicking mesh liner, and side-stretch panels conform to your body and allow for maximum body movement. The Ion heated baselayer has integrated, concealed heating panels powered by sturdy yet light-weight 7.4-volt fine heating coil system. The 7.4-volt system has two heating elements on the back that add heat to critical areas that keep your core warm. The Ion’s 7.4-volt heating system can provide temperatures ranging from 135°F on high to 90°F on low. On high, expect 2.5 hours of heat, and on low, the Ion can provide heat for up to 10 hours! The Ion has two ways to adjust the temperature. First, the built-in touch control button. With a simple button push, you can select from four heat settings. Second, we’ve incorporated Bluetooth® control with our MW Connect™ app. Through the MW Connect™ app, you can quickly toggle through all connected Fieldsheer® devices and adjust individual heat levels to your liking. MW Connect™ allows you to get real-time updates on battery levels and update your garments when new firmware becomes available. All day, any weather, the Ion heated baselayer shirt is a versatile insulating layer that keeps you warm all winter long.