Polartec@ Power Wool™ is all non-mulesed and raised using the 5 Freedoms Rule. Polartec® Power Wool™ Is A Nylon Merino Bland That Exceeds The Durability Of Traditional 100% Merino Fabrics, which makes it ideal for next-to-skin apparel. Warm enough to wear alone and thin enough to layer, the Merino Hinged Headliner is breathable, odor resistant, and offers amazing wicking for its weight. With an incredible warmth and comfort factor this is the ideal liner that fits easily under hats, helmets, or any other headwear.Recommended for: wearing alone on cold days or layering for extra warmth.