This bag holds so much more than the others I’ve looked at. Internal volume is plenty big (soda can for scale) – plenty of space for a couple of big 3″ D-ring binders to fit just fine. I’m impressed by how the closures work as well – the zipper looks very water-tight, and I think would resist water exposure to spray or minor immersion just fine. The velcro fasteners are sturdy, and the design allows for some overlap to protect the closures. I haven’t tested the lock at all – I probably won’t use it, and wasn’t a feature that I was interested in.