The outer layer, or shell, is one of the most important items in any adventurer's kit, as it is specifically designed to protect you from wind, rain and snow. When choosing an outer layer, it's important to look for a membrane-based garment that uses GORE-TEX, eVent or similar technologies. Membrane technologies block water from entering, whilst allowing water vapour (or sweat) to evaporate through the garment. For drier conditions, a non-membrane windshell-style jacket will offer better breathability, but keep in mind that it won't protect you from a heavy downpour! For a more detailed look at outer layer shell jackets and some tips on selecting the best one for you, check out our guide here.