You've got the right insulation. You've paid for waterproofing. You've checked fit and wind resistance. Then you're standing in -5°C on a ridge, and—despite everything—you're freezing. The culprit? An ordinary collar that lets cold air circulate directly around your neck. Research on thermal ...

Your jacket is rated 800-fill down. Your friend's is 600-fill. You're both standing on the same cold ridge. Your friend feels warmer. The difference isn't the insulation. It's the fit. Thermal comfort doesn't depend solely on what's inside your jacket—it depends on how much of that ...