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. | Seirus Merino Hinged Headliner Hat