The Milwaukee Heated WORKSKIN Midweight Base Layer Kit is powered by a REDLITHIUM USB Battery with carbon fiber heating elements to create and distribute heat to the chest and back. A 1-touch LED controller allows users to select from 2 heat settings, delivering ideal heat for any environment. The Quick-Heat function allows users to feel heat 3X faster in the chest and upper back heating zones. Combining a double-lined polyester body and fleece-lined arms, the heated midweight base layer provides a versatile layering piece for total body warmth. This battery heated shirt features raglan sleeves and seamless shoulders for an improved range of motion and comfort while working. This midweight next-to-skin base layer kit includes one Medium Heated WORKSKIN Midweight Base Layer (405B-21M), one RLUSB 3.0Ah Battery (48-11-2131), one REDLITHIUM USB Battery Controller/Charger (50-59-2005), and one 3 ft. Micro-USB Cable and 2.1A Wall Charger (48-59-1202).