Future Now: Argon-Filled Klymit Vest

A new fill technology that will keep you toasty warm.

If George Jetson climbed peaks, he wouldn't settle for some prehistoric 20th-century fleece to keep him warm. No, the man of the future would don this argon-filled vest, and he'd stay toastier than a cat in a microwave. How do we know? Because we tested just such a garment–from an innovative new company called Klymit–in subfreezing temperatures on 14,259-foot Longs Peak, and the gas-filled vest reflected body heat like no other jacket we've ever tried, not even the fluffiest 900-fill down.

To inflate, connect a small argon cylinder (argon is an inert gas with extremely low thermal conductivity) to a tube in the left pocket that leads into the jacket's sealed chambers, then pull the trigger to inflate.

The vest ($150) comes with three recyclable (non-refillable) cylinders, similar to CO2 cartridges used by cyclists. Each cylinder is good for two to five fills, depending on vest size and the amount of insulation desired. Our take: While the insulation is truly futuristic–and legit–the vest is not yet packable or practical enough for backpacking. Unlike down, argon isn't compressible, so you must deflate the vest after each use; we burned through two canisters in one day on Longs. klymit.com