The best way to beat the chill To really stay warm, you need to concentrate on your foundation garments. The soft Thermolactyl polyester & viscose mix fabric of our vests keeps you cosy by conserving your own body heat by drawing sweat away from your skin minimising evaporative cooling to keep you dry & warm. The 2 pack of mens T-shirt style vests are thin & fine enough to wear under your shirt & are perfect for all manner of outdoor activities. Available in S, M, L, XL & 2XL.