Stylish warmth from base layer to outer layer. The Proton Heated Baselayer Shirt features a midweight printed knit design with a soft lining, flat stitching, and a 1/4 zip for easy ventilation. In-seam thumbholes add a secure fit, while 3 heat zones deliver consistent core warmth. Whether layered under your winter gear or worn on its own, it&';s the perfect blend of comfort and performance.