At Lands End we believe comfortable kids are happy kids. That s why we select breathable stretchy fabrics when designing our kids clothes for your active boys and girls. The Boys Thermal Base Layer Long Underwear Thermaskin Crew Neck Shirt is no exception. A quality spandex-blend base layer shirt designed with stretch and flexibility for all of their big adventures outdoors during tumultuous winter temps so they can enjoy their snow days to the max.