In use, the Double Diamond is perhaps not perfect, but it is unique. Users have the choice of filling the vest with either argon gas via small compressed cartridges and a compact inflator, or with regular air via a small bulb-pump stowed in the pocket. I opt for the regular air because, well…I'm too cheap to pop for the argon, although I will admit it works much better. When inflating the vest, it does get overly rigid if you're heavy handed with the pump. Anyway, a little air is all you need to create the warming effect. The amazing aspect of the vest is how well engineered the air channels are so the entire surface of the jacket inflates evenly. The channels don't impede movement too much, but it does tend to feel a tad like an apparatus and less like a layer of clothing.
When deflated, it feels like any other outer layer, and actually retains a good bit of heat. When removed, deflated, and stowed, it's not quite as small as I would have expected, but it isn't any bigger than a down vest. Having worn it a number of times, I will also say it has worn well with no damage or leaks. Its certainly well made like all Klymit products.
The final report is a bit hit or miss. For genuine outdoor activities like skiing, snowshoeing, ice climbing or other pursuits, I'm not sold on it. It's chunky feeling. It makes me feel like I'm wearing an exoskeleton. The inflation is a bit of a hassle as well as expensive with the argon gas. That said, I have found a great application for it under my motorcycle jacket. I inflate it for early morning temps for maximum insulation, and as the sun warms me, I reach in my jacket, expel the air, and a layer magically vanishes…sorta. It is a far less complicated alternative to electric gear on the bike. Because motorcycle riding doesn't involve dynamic torso movements, I don't even mind the stiffness.
The final verdict? Maybe this isn't the solution Nate had hoped for. I'm still reaching for a down vest on a regular basis and the novelty of inflating my vest for friends has long since abated and watching them try it on has become a little tiresome as well. I applaud Nate for the innovative approach, but this one*––is not for me.
*I may not love the Double Diamond, but Klymit does make amazing sleeping pads. The Inertia XL is one of my favorite innovations of the year.