When the mercury drops a little more, go for the heavy weight version of our MTP Polartec underwear to keep your child warm and toasty. This Heavy Weight 1/2-zip mock neck top is 100% polyester that's fleeced on the inside to trap extra warmth. It has a flat jersey face and uses ScentEliminator technology to control odor-causing bacteria. Imported. Sizes: XS-XL.