EPS + Merino wool helmets use the same EPS foam for impact protection, but add a soft merino wool covering against your head. The merino naturally regulates temperature, wicks moisture, and resists odors — so your helmet stays fresher and more comfortable over long days on the mountain.
This combination makes the most sense if you run hot or cold easily, ski multiple days in a row, or just prefer natural materials against your skin. The wool helps take the edge off that clammy feeling you get with bare foam after working up a sweat.
Keep in mind that the merino doesn't change the helmet's impact protection — that's still handled by the EPS foam underneath. You're paying for comfort and odor control, not additional safety. If you're on a budget, a standard EPS helmet with a removable, washable liner pad will get you similar benefits for less money.