Rocky cotton knit thermal underwear for boys set is designed for comfort with Polyester wicking microfibers. These boy's thermal underwear are stretchy comfortable. WONDERFULLY WARM: Rocky's thermal underwear for boys is perfect for use underneath formal or casual attire at work or for a day out, or the thermal underwear can be worn as comfy pajamas on cold, chilly nights. PREMIUM GRADE FABRICS: Rocky thermal underwear for boy's is made from 55% Cotton and 45% Ultra-Soft Polyester, these thermal long johns have the perfect blend of comfort, warmth, elasticity, and moisture protection. MOISTURE WICKING: Designed to keep you dry, this long-sleeved shirt and long pants are made to be wick away sweat and other moisture, this thermal underwear for boys set will do its job no matter how active you are. BASE LAYERS: When going out to jog, run, bike or cycle in the cold, make sure to use the rocky thermal underwear for kids set under your clothing to keep warm and cozy in freezing cold climates or bad weather. These thermal underwear are stretchy & comfortable.