The latest evolution of our base layer spinning technique utilizes high quality micro-fibers to produce coiled or "crimped" threads. Compared to traditional fibers, the refined microfibers present in ZEO-LINE® feature greater surface area and smaller air pockets to better trap air, yielding superior heat retention. Featuring a three-layer knit structure, maintains an air-layer between dual fabrics. The layer closest to your skin pulls moisture away and moves it to the outer layer allowing the layer of air to maintain more consistently warm temperature.