Forget diamonds. Good quality women's base layers are your best friends when out on the hills or in the woods. They'll wick away sweat and keep you dry and comfortable, keep you warm, and if you choose a merino wool material, they'll also stop you from getting smelly even on multi-day trips. Now that's the kind of buddy we could all use! Choose from comfy bras that won't chafe under the shoulder straps of a backpack, cool and dry pants, and warming expedition-weight tops. If you're looking for warmth without weight, Patagonia Capilene 4 is superb stuff.