A Removable Storage system provides two classes of media pools: system and application. System media pools include free media pools, unrecognized media pools, and import media pools. Removable Storage creates one free, one unrecognized, and one import media pool for each media type in your Removable Storage system.
You should bring one even if you don't plan on wearing it. Parka/Raincoat Hikes will never be planned in the rain since it really is no fun to hike in bad weather. Since the weather is very unpredictable it is best if everyone brings rain gear. Toilet Paper. Generally a bathroom will be available at the base of a mountain as well as at an AMC cabin on the mountain.
I suggest reusing the plastic bottled water bottles, they're a good size and very lightweight when empty, and you can easily bring 3-4 for a longer hike. Water should be the heaviest thing in your pack and preferably easily accessible while you're walking.