David Yaghmourian, 30, was visiting a friend in Portland and the pair were just finishing a backpacking trip when they separa. These are the most popular backpacking packs sold at REI and they’re an excellent choice for warm-weather trips lasting 3 or more days. 50-80 liter packs are also used for backcountry skiing, for day trips, overnighters and sometimes 2-night trips. Really the best way is to go in and…