|Duofold Youth Varitherm First Layer Ankle Length Thermal Bottom KFL6 fiber content is 100% Polyester. Duofold Youth Varitherm First Layer Ankle Length Thermal Bottom Varitherm First Layer is an all polyester lightweight single layer that incorporates all the features that Varitherm base layer wearers expect, including moisture management and stretch fabric. Features: Excellent moisture management. Stretch for ea. Duofold Youth KFL6 comes with 1 Thermal Bottoms per Pack.