The N-Ferno 6870 Thermal Mouthpiece has 2 layers of insulation with a cotton shell and a polyester fleece liner to provide comfort, warmth and face protection in extremely cold weather work conditions. This thermal winter face mask is made to fit most N-Ferno Winter Liners (liners sold separately) to double up the warmth on those frigid jobsites. The shell design prevents the mask from being sucked into the mouth for plenty of breathing space and protection from the cold air.