The Hot Chillys Kids' Pepper Bi-Ply Crewneck Top is constructed with two layers of fabric connected back-to-back with open spaces between the layers to trap and hold warm air. This kids' thermal top is also knitted with MTF soft spun polyester fibers that transport moisture away from the skin to keep you warm, dry and comfortable. Pepper Bi-Ply is a tried-and-true favorite choice that makes for a soft, comfy youth base layer shirt while protecting against the cold.