External frame packs– Best suited for heavier loads on open, even trails through easy-to-moderate terrain. External packs place the load over your body’s natural center of gravity. This allows you to bear the weight comfortably, without stooping and without undue expenditure of energy. An external frame pack also keeps space between you and the load, which accomplishes two things: it allows good ventilation to keep you cool, and it helps make even a heavy load more comfortable while you hike.    

Internal frame packs– Designed for uneven terrain and narrow trails, where a hiker needs more agility. Balance and stability are essential on uneven, narrow or slippery terrain. An internal frame pack keeps the weight of the load tight against your body, giving you more freedom of movement. If you’re into off-trail adventures, an internal frame pack should be a consideration.