Polartec Alpha Direct was originally developed for the US military as an insulated fill alternative, it has taken off in popularity with ultralight hikers as a standalone fleece replacement. By placing patented low-density fibres between air permeable woven layers Polartec® created a more efficient fabric for regulating warmth and transferring moisture. This advancement increases thermal adaptability in changing conditions and different phases of physical activity. Alpha is also hydrophobic, so it won't absorb moisture even if you start to sweat. Alpha is certified Standard 100 by OEKO-TEX®.