Mens Thermal Underwear Top Heat Holders Thermal construction holds more warm air close to the skin keeping you warmer for longer. This set of thermal underwear is the perfect set for layering as of its easily fitting design for under your clothes for a smooth slim fitting thermal base layer for the colder days where one layer isn\'t enough! This thermal underwear set has a TOG rating of 0.39 adding that crucial extra layer of warmth. The higher the TOG the better the garment will keep you warm. The technical construction of this thermal underwear along with its supportive fit have been designed so that it effortlessly shapes and works with your body\'s natural contours providing the best fit possible - making it hardly noticeable under your clothing. The base layer is made of a lovely soft modal fabric which helps to add that extra bit of warmth and makes it extremely soft for added comfort to the garment. This top part of the set has a seamless body helping to reduce the risk of irritation - meaning all day comfort while being worn. The thermal underwear set comes in 3 colours (Black Grey and White) and there are matching long johns/leggings also available in separate listings. We also offer womens sizes/colours.