This is a great option for a 72-hr bag. I have two of these packs: one remains indentured with my Skycrane "backpacking" equipment, the other was bought separately so I don't have to constantly move gear back and forth for "go bag" purposes. I use Eberlestock 2-liter water bladders for these bags; they fit perfectly inside the interior sleeves, and haven't failed me, yet. I do recommend that you add Eberlestock's waist belt if you're hauling much more than a day's worth of gear/supplies- I also use their "Endo" frame accessory, as my pack can run a bit heavy once I've filled up with water...The pack has Molle webbing everywhere, inside and out, and has thoughtful pouches/pockets in all the right places. Your hydration tube(s) have three resealable ports at the top of the bag for your placement preferences. The drop-leaf opening to the main compartment makes packing and locating your equipment a breeze, and also provides Molle webbing on both sides- adding serious customization options. Eberlestock thoughtfully provides integrated Velcro strap keepers to clean up stray/excess material, too- no need to buy those separately.The shoulder harness and ventilated padding are superior to any other system I've used: all-day rucking comfort, even with a full load-out. Best of all: this pack stays put, once slung; bouldering, etc. won't cause any hot spots with this well-engineered harness system.The Little Brother is perfectly sized for three day excursions, provided you've done your load-out homework and aren't packing for a nuclear winter. It's narrow design gives you plenty of back/shoulder space to mount additional pouches/gear to the pack's exterior- while still leaving room to carry a slung rifle. Of course, you also have the option to use the rifle scabbard sleeve, as well.I'm a big fan of Eberlestock's products. They do cost more, but these packs are built to last... my knees will need replacing before I need to replace this pack. This seller was great on all counts, as well- and was quicker to ship than buying direct from Eberlestock. Be safe and keep your powder dry, my friends.6/3/2016 Update: I highly recommend adding the small Eberlestock Gossamer Frame accessory for this pack, for a much more comfortable fit and vastly improved weight distribution if you're hauling heavier load-outs- I added a review for the Gossamer frame that includes the details... With this accessory, I'm enjoying the best fitting, easiest wearing pack I've ever used.