. 88% Polyester, 12% polyurethane . PREMIUM GRADE FABRICS: Using functional AeroWarm fabric, This high quality fabric is thin and lightweight, but it is 35% lighter than conventional fiber and superior in heat insulation effect than cotton or wool material by 20%. It fit perfectly and keep warm in cold temperatures that almost hit freezing. There is a micro fleece lined, so it can be worn softer and warmer. . 2 PIECE SET: MiNi-K thermal long johns have the perfect blend of comfort, warmth, elasticity, and moisture protection. This long-sleeved shirt and long pants are made to be wick away sweat and other moisture. Also, it has an anti-static function that makes it easier for children to wear it. . FREEDOM OF MOVEMENT: Our long underwear are made of a four-way stretch design that enhances your child’s move freely in any direction. . GREAT FOR BASE LAYERS: When going out to jog, bike or hiking, camping in the cold, make sure to wear MiNi-K thermal set for children under your clothing to keep warm and cozy in freezing cold climates or bad weather