I'm going out of the country soon, and I wanted a pack that would be somewhat tamper resistant. I almost ordered the 20L pack, then read that it has no organizational pockets inside of it at all. So, I ordered this one. I ordered the gray pack, since everything else I have is black. *wish they had the Tabasco one in the 25L.. This is the biggest backpack they have, and it is the same size as a school backpack they have at department stores. Don't expect to pack 3-4 days worth of clothes in here. Maybe you could, if you had NOTHING else. I'm going to put my digital SLR in here, inside of a drysack - then some lite raingear, some sandals, sunscreen, towel, etc etc.. Nothing major. I don't know if this pack is waterproof or not. It feels like it is, but, I'm not going to push my luck. The zippers are very limited on how far they unzip - which is kinda the point. If they went ALL the way down to the bottom of the sack, it would be easier to pry apart I'd think. In the main compartment you can stick a 13 inch laptop into the special little velcro-ed section, and still have a good amount of room to go. In the middle compartment, there are some small velcro pockets, and another good amount of room. Then the outer pocket part, is pretty small, you can diagonally squeeze some maps in there, and maybe a few other really small things. The straps are super comfortable and padded, and the back part of the pack (that touches your back) is super padded too. It has two pockets on the outer sides that you can stick water bottles in also. Very nice bag - doesn't look TOO tourist-y either. The picture makes it look kinda tall and funky - but, it's way smaller than one may think. I can't imagine the 100 series holding more than maybe a sandwich and some AAA batteries.