Looking to add warmth to your outdoor activity? Then Fieldsheer heated Baselayers are a must for you. The Fieldsheer Bluetooth-Enabled Primer Plus heated baselayer shirt offers light-w8 performance and our integrated Mobile Warming heating system. From skiing, hunting, hiking to running or just working outdoors, the Primer Plus Shirt complements your outerwear to keep a warm core. Its moisture-wicking, warmth, and stretch features make it a versatile heated baselayer in the winter, or a standalone shirt during outdoor activities in the Spring and Fall. The Primer Plus is made from a 4-way stretch anti-microbial 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 form fitting movement. The Primer Plus heated baselayer has integrated, concealed heating panels powered by our sturdy yet lightweight 7.4-volt Mobile Warming Heating System. The 7.4-volt system has 3 heating elements, one on the back and 2 on the chest, that add heat to critical areas that keep your core warm. On high, expect 2.5 hours of heat, and on low, the Primer Plus can provide heat for up to 10 hours! The Primer Plus has 2 ways to adjust the temperature. First, the built-in touch control button. With a simple button push, you can select from 4 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 Mobile Warming 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 Primer Plus heated baselayer shirt is a versatile insulating layer that keeps you warm all winter long.