Mirra Base Layer Top The Mirra Top women's thermal base layer is made of a highly breathable material composed of microscopic fibers, quickly removes moisture, is quick-drying and highly breathable. The specialty is the content of silver nanoparticles, which reduce odor. Pleasant flat seams are a matter of course. Mirra Top is made from 92 % polyester and thanks to 8 % elastane is flexible and will not restrict your movement.