Rayon from bamboo softens the feel against the skin, and merino wool adds odor resistance, in the 260gm blend that makes up the Le Bent Midweight Mock Neck Top. This midweight merino base layer suits alpine starts and long runs. What Our Gearhead(R) Experts Are Saying:"Pre-dawn lift lines had me zipped into a shell before I got there, and the unstructured mock neck sat flat under the collar. I wore it all morning without thinking about it."