Mil-Spec+ Military Polypropylene ECWCS Underwear Top & Bottom Full Combo Set (Black, Small) - Combo Set includes Thermal Balacalva, Thermal Booties, Thermal Bottoms, Thermal Top, Thermal Neck. - Military ECWCS Polypropylene Wicks the moisture away from the body to the outer garments, where the wearer will not be affected and will stay warm and dry. - Military weight polypropylene, combined with its fleeced lining, offers high levels of insulation against the outside cold in addition to providing an even and steady comfort level. - Thick and soft - the warmest underwear you can own!