With a truly long list of features, the Altios is definitely the most tricked out helmet on the market. For ice climbing you can attach the VISION face shield. If you're nailing up El Cap in August, you can move around the padding to open up or close vent holes. The mesh layer is removable to make the helmet fit better with a hat or increase ventilation. You can also use the ADAPT clip for a single-point attachment of a Petzl Tikka or Zipka headlamp.
Beyond the long list of features, most people found the helmet very comfortable. This was the only helmet with a mesh layer on top to disperse the pressure across the entire top of your head. This is in contrast to most helmets where you feel "pressure points" if you push down on the top of the helmet. Like all Petzl helmets, you can adjust the chin-strap while wearing it. This on-the-go adjustment is convenient during long belays or extended hikes, providing quick and easy ventilation. This feature isn't common among competing helmets, and it's a big plus for this helmet.
We prefer low-profile helmets, ones like the Elios, Petzls streamlined plastic helmet. The Altios floated just too high, which made the helmet top heavy and more likely to roll back when looking up while belaying or searching the path ahead. You can remove this mesh layer to make the helmet sit closer to your head. But if you are going to mostly wear the helmet minus its mesh, we would rather have the Elios, which costs $24 less.
While we do not rate helmets on looks in our comparison table, most people felt the fact that the helmet sat so high was not a flattering look.
This is an all-around helmet. It is great for winter and summer climbing, hard nail-ups and alpine. Petzl uses a 1,2 size system on the Altios. Size 1 is small to medium. 2 is medium to large (this applies to its harnesses, too), which means it is not as adjustable as the Ecrin Roc if you are looking for a helmet to teach with.
Size 1 is $80 and size 2 is $90 (Size 2 fits most adults). This makes it one of the most expensive helmets we tested. It is durable, so over time you will get your money's worth. And it isnt a bad price tag if you really value all the features that Petzl packs into this workhorse of a helmet. But if you don't want all the features, there are four other highly rated helmets for $60 to $65.