Powered by REDLITHIUM™ USB Battery TechNlogy, Milwaukee Heated WORKSKIN™ Base Layers use carbon fiber heating elements to create and distribute heat to the chest and back. Combining a double lined polYter body and fleece lined arms, the midweight base layer provides a versatile layering piece for total body warmth. Raglan sleeves and seamless shoulders allow for improved range of motion and comfort while working.