The Bottom Line: A stylish and sturdy helmet that gives you no excuse to not wear it when you go climbing.
The Mammut El Cap is adjustable using a slider bar located instead of a click wheel to tighten. It is comfortable to wear all day, but it is not as lightweight as other recent foam models. One of the main distinguishing features is the little visor, which helps block the sun if you aren't wearing a hat beneath your helmet and is also handy for keeping a headlamp in place. For female climber with long hair, there isn't a pony tail adjustment at the back, which models like the Petzl Elia have. But this is easy enough to navigate around.
The El cap has two big ventilation slots in the forehead and more on the sides. I wore this in the summer with a hat underneath, and it felt comfortable. It can get a little chilly in the winter, but wearing a beanie underneath fixes that issue.
The headlamp attachment doesn't look like it will be sufficient, but it kept my headlamp on, and I never had an issue with it. While the visor helps hold a headlamp in place, it is worth mentioning that a headlamp's beam is partly blocked by the visor, so there will be a small dark spot in the projected light.
The Mammut El Cap is a sturdy and stylish helmet that provides good ventilation and sun protection, and it is a good choice in spite of its slightly heavier weight profile.