Thermal knit material helps maintain newborn's body temperature and wicks away moisture from newborn's head.WARMING - Mars Wellness Booties and Set were designed with the comfort and health of the baby in mind. The Thermal Knit Material in the Hats maintain the newborns body temperature and wicks away moisture from the head. The Booties are made from a plush terry cloth material to keep feet and ankles warm. FITS MOST - The Mars Wellness Booties and Hats for newborns comfortably fit most newborns and babies. EASY WASH - Mars Wellness Booties and Hats are easy to wash. Simply hand wash or machine wash on delicate cycle. Lukewarm water with mild detergent, do not use bleach. Tumble dry low heat. PREMIUM MATERIAL - The Mars Wellness Booties and hats are Latex Free and manufactured with only the best quality in mind. NO RISK - Here at Mars Wellness we stand behind our products. If for some reason you are unhappy please reach out to us right away.