Thermal underwear budget base layer unisex long sleeve top by Sub Zero are the ideal starter range for anybody who is new to cold weather outdoor activities or who wants a cheaper alternative to the Factor 1 & Factor 1 Plus base layer thermal underwear ranges. Our Polyester/ Viscose fabric is knitted in the UK & we have it brushed on the inside face to provide a super-soft fleece lining next to the skin. For a more detailed size chart please visit our technical information pages.