The Mobile Warming Bluetooth-enabled Primer heated baselayer shirt is designed for the outdoor enthusiast to keep your warm core. Its moisture-wicking, warmth, and stretch features make it a versatile baselayer in the winter, or a standalone shirt during outdoor activities. The Primer is made from a four-way stretch anti-microbial 88% polyester and 12% 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 Primer heated baselayer has integrated, concealed heating panels powered by sturdy yet light-weight 7.4-volt Far-Infrared Heating System. The 7.4-volt system has 2 heating elements, one on the back and one on the chest. It 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 for up to 10 hours. The Primer 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, Bluetooth control with a MW ConnectTM app is available. Through the MW ConnectTM app, you can adjust individual heat levels to your liking. MW ConnectTM allows you to get real-time updates on battery levels and update your garments when new firmware becomes available. Includes the 7.4V (2200 mAh) Lithium-Ion battery and a micro USB charging cable. You can expect up to 10 hours of heat per charge.