The Peruvian looks like a standard four-panel crown construction beanie, of which there are many good ones out there. What sets it apart are four critical features for serious backcountry use. First, it's made out of GoreTex WindStopper to keep your ears attached to your head in alpine conditions. Second, the earflaps are long enough to cover the most elephantine of ears. Third, the earflaps can be secured by a chin drawcord, which for some reason is rarely shown in the pictures, but rest assured it's there.
Finally, the Peruvian is slim enough to sit seamlessly under a helmet or tight hood. Like all WindStopper headgear there's a certain deadening of sound with the earflaps down. If you really need to hear stuff, the earflaps easily fold up either inside or outside the hat, thanks to the elastic trim. The Peruvian is a fantastic hat, and at only 1.6 ounces there is no excuse to leave it behind next time you're headed out for an epic.