The Merino Heated Baselayer Shirt allows you to keep going no matter what the conditions throw at you, and by maintaining a healthy temperature, you reduce fatigue, muscle soreness and decrease sensitivity. Fieldsheer’s Performance Series delivers unparalleled performance and rugged durability without sacrificing comfort or mobility. Since 1978 Fieldsheer has been a leading manufacturer of outdoor apparel, men’s heated clothing and women’s heated clothing. We know that conditions can change rapidly, and our Merino Heated Baselayer Shirt lets you adapt and stay warm in any environment, from arid desert conditions to high Alpine timberlines.