This is a fantastic workhorse of a pack. I have used one all over the globe, weighted down with cold weather gear and ammunition and weaponry and radios and all things imagineable. You can drop it fully loaded off a 5-ton truck and it just doesn’t care about it. Damned near indestructible. The suspension system isn’t fancy, but under extreme loads it is way better than any crazy-expensive civilian pack I have yet to encounter.
The inside is one big compartment. The top flap has a velcro-closed opening for holding maps and such. There are three large and three small external compartments, which gives you lots of space and options for organizing the small stuff and having easy access to things. You can strap lots of junk to the pack, and to the frame underneath the pack. You can also strap stuff on top of the pack, which is what I have done with sleeping mats and wet weather gear and weapons.
You can get these things online from military surplus outlets. Make sure you get a no-kidding US-made, US military surplus pack — not one of those Chinese knock-offs. And make sure you get the large ALICE pack frame to go with your large ALICE pack.