Warm Layers That Pack Down to Nothing

An insulated jacket is the one piece you will never want to carry until the moment you need it. The best ones pack to the size of a grapefruit and save your life at a cold summit.

Look for the details that matter.

• Down packs smallest and warmest but dies when wet
• Synthetic stays warm damp and costs less
• A hood adds serious warmth for a few ounces
• Stash it in its own pocket so it is always ready

Buy the packable layer before the trip that needs it. The summit is always colder than the forecast promised.

Keep the packable layer accessible, not buried at the bottom. The summit wind hits fast, and the jacket only helps if you can reach it in ten seconds.