Strategically placed heat zones in the chest, kidneys and base of neck provide warmth to critical areas; Seamless construction creates added comfort and reduces friction on the skin; Rechargeable 7.4 lithium-ion battery and wall charger included; USB outlet on battery can be used to charge devices in the field; Low-profile, durable and comfortable carbon-fiber heating elements; 3 adjustable heat settings with easy-to-access, LED heat level selection button; Athletic fit allows for easy layering; 60% Polyester/23% Propylene/17% Elastane; HydroWick high-performance hollow wicking fibers reduce moisture; Treated with Polygiene Odor Control and Odor Crunch