18,5 micron is an annually renewable, 100% natural product. It is durable when in use, yet recyclable and biodegradable at the end of its life cycle.  This 18,5 micron fiber will absorb perspiration without making you feel damp and uncomfortable, with the added benefit of being naturally shower repellent. Absorbs moisture and generates heat.  Easy care and naturally odor free.  Woolmark® certified.