My canopy research project requires me to climb 10 trees a day once a week, so I need something that is efficient, organized and rugged. I use a Kelty 65L external frame pack. I've been using this pack for both my research and rec climbing for three years now, and I absolutely love it. An external frame is especially nice because it holds its shape when putting gear away. It doesn't flop around as some internal frames may. The main compartment stores my rope, throw line, saddle and helmet. The bottom compartment, although looks small, is actually pretty roomy. It stores my friction saver, lanyards, prussic cords, webbing, gloves, accessory cord etc. The side pockets are convenient for accessory gear like carabiners, micro-grabs, throw weights, water bottles etc. Even with all this, there is still room for more if ever needed. I would definitely recommend an external frame for climbs that require hiking through the woods.