|Duofold Youth Varitherm First Layer Long Sleeve Thermal Top KFL5 fiber content is 100% Polyester. Duofold Youth Varitherm First Layer Long Sleeve Thermal Top 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 KFL5 comes with 1 Thermal Tops per Pack.