I been learning a lot about helmets lately. The Petzl Alveo is nearly identical to the Kask (except for the accessories, which the Kask has more of). They are both the same weight (12 oz compared to 16-18 on most others) and both are compatible with similar half-face plastic visors and the same ear muffs. The really big deal about these helmets is how they absorb an impact by deforming the styrofoam liner inside (like how a bicycle helmet works). This is different from how all the other helmets absorb an impact by deforming the plastic shell (like when you kick a tire - it pushes a bubble in and then back out). This is a big deal because the Alveo and Kask helmets will only withstand a single impact which damages the styrofoam liner and must be replaced afterwards, whereas the other helmets will usually withstand multiple impacts before they finally give in. I think this was the reason for all the negative feedback over at TB last year, because the Kask helmets were the first to work like this. Since they don't have to maintain a minimum distance away from the skull in order to allow an impact to press a bubble into the plastic shell, the Alveo and Kask helmets fit closer to your head and are thus more stable and less wobbly, especially when wearing ear muffs. So most people report that they fit and feel better. But on the other hand, the space above your head inside the shell is mostly filled up with insulating foam, so they can be warm in spite of all the vent holes. Petzl has also recently improved the way their helmets adjust, with two ratchet knobs now instead of just one. This "centerfit" adjustment system allows the user to keep the skull in the middle of the shell, so it isn't closer in the front and farther away in the back like is common on Kask helmets. This gives Petzl helmets the same impact protection all the way around, so there is no weak spot on the forehead. Personally, I prefer the Pacific Kevlar helmets. All plastic shell helmets should have a lifespan of 3-5 years, while the Pacific Kevlar might last forever. This is because plastic gets brittle in sunlight, causing a plastic helmet to get weaker over time. Also, the Pacific Kevlar helmets are the only ones with replaceable suspension systems, so I can refurbish mine when it starts to stink.
Whew! I think that's about it.
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