Fieldsheer Men's Merino Heated Base Layer Pants - Fieldsheer knows that conditions can change rapidly, and Fieldsheer's Merino Heated Baselayer Shirt lets you adapt and stay warm in any environment, from arid desert conditions to high Alpine timberlines. Heavyweight Base Layer Multi-Zone Heat Elements: 2x Inner Thigh & 1x Upper Waist Bluetooth Control with MW Connect Integrated Touch Control Button 4 Selectable Heat Settings 7.4volt Rechargeable Lithium-Ion Battery Up to 10 Hours of Power Per Charge Universal USB Charging Input Style: MWMP21010321