- Bombas undershirt

mauve. Meet Merino Wool. It's a naturally soft fiber that's guaranteed to keep you warm when it’s chilly, cool when it’s hot, and comfortable in pretty much every situation. Even better, our Merino Wool shirts are blended with TENCEL™ Lyocell, a fiber known for its cooling, quick-drying, and smooth-against-the-skin properties. And since you’ll be layering this under everything you wear, we added a thumb hole right in the sleeve cuff. It’ll keep your sleeves from riding up your arm, plus it’s just a fun little pop of color.