17.5 Micron Merino wool
Here's what other sites are saying:
Forget your fears about itchy wool-the Stoic Merino Crew Shirt is a whole different beast. Employing 17.5-micron Merino wool from New Zealand, the Merino Crew Shirt ensures comfortable, dry days whether you're out for a mid-January dawn patrol or an autumn ride down the single track. Merino transfers moisture while your sweat is in its primary vapor form, so unlike most synthetic fabrics the Merino Crew Shirt begins to pull moisture away from your body before your shirt becomes saturated. And since wet usually means cold in the backcountry, warm Merino is the way to go. The athletically-fitted Merino Crew Shirt feels great against the skin so you can wear it during your ride and then to the pub, and your post-ride car mates will thank the powers that be for Merino's natural odor-shunning properties. A reflective logo hit on the Merino Crew's front neckline ensures a little more safety during your evening runs, and the thumbholes at the cuffs take the bunch out of layering.
- Backcountry Outlet refers to the men's version