Your complete guide to Merino wool.

What is Merino wool made of? Proteins composed of amino acids and natural compounds. Merino wool is a natural, renewable fiber—meaning one sheep can grow four to five pounds of wool per year. Plus, this fiber has evolved over the years to keep sheep comfortable in harsh environments. These happy animals hang out in temperatures that range from 5 degrees to 95 degrees—no problem. It’s a pretty amazing fiber.

What is Merino wool really good at? Helping keep your body at a stable temperature. When it’s cold outside, the natural crimps and bends in its fibers trap air, insulating you. When it’s warm outside, it transports sweat quickly away from the skin, helping to keep you cool and dry.

This benefit of wool gets a bit technical—so bear with us. Merino wool transports sweat and moisture away from skin as a vapor. Merino fibers are inherently porous. They’re composed of little plates that moisture vapor can get in between—meaning you're not left feeling wet, cold, and clammy after a workout. Synthetic fabrics are not porous. They usually wick sweat when it’s already a liquid, and then your body has to heat it up to evaporate it—making you feel clammy in colder weather. Merino takes a step out of the process, which helps you stay warm and dry when you’re moving and playing outdoors.

Sometimes it’s really cold outside and you need to layer. By using all Merino wool when you layer, you create an escape route for sweat and excess heat. Each layer of Merino works to transport sweat away from the skin to the outside of your gear while it’s still a vapor (pre-sweat)—helping to keep you warm and dry. Throwing a synthetic layer in there mucks up the sweat-vapor escape route and creates a detour that might increase your chances of getting cold and clammy.