The N-Ferno 6435 Midweight Long Sleeve Base Layer Shirt is designed for comfortable warmth in cold conditions. Made with a stretch performance fit that warms core temperatures without overheating or restricting movement during strenuous activity. The 240 g polyester-spandex performance material provides warmth without the constricting or bulky feel often found with heavyweight base layers. The fabric is smooth and stretchable for easily layering under sweatshirts and jackets, plus thumb loops and a long tail for full coverage that stays in place. Unlike other base layers, this shirt is designed to sit slightly looser on the skin to enhance breathability and mobility while also preventing overheating providing an air gap for additional insulation. Raglan sleeves with wider underarms also make for full range of motion.