It's a medium sized bag like I was expecting it to be. For those like me that really can't mentally picture the size of the bag by measurements, the large compartment can roughly hold six or seven full mre's packs. Maybe even eight if you push it, I know no one will put that many in there but just for a size est. The second largest compartment fits notebook size items, you can place a pack of 500 sheet printer paper in there with room to spare. the third compartment is like the size of a fannpack. Maybe you could jam one full mre in there. The last compartment is like a school pencil bag. There is also a compartment for a water bladder which is closed in on top be velcro. There are two molle straps on either side of the pack. Two on the third compartment, one on the fourth (smallest) compartment and lots of buckles and straps to hold everything together. Over all the stitching seems like it will hold and the inner lining is coated or made from a material that appears will repel water. I don't expect it will keep everything dry in heavy rain but in a light rain it should keep the contents dryish. There mare also webbed pockets in the three largest compartments that you can put random things into. Overall a good pack for hiking and such.

Pros::
- Flexible size: Compresses very thin for lightweight everyday carry, expands for full high school / college use;
- Weather resistant: Keeps contents dry in snow indefinitely and for 3 hours in light to moderate rain;
- Modular: All of the MOLLE / PALS webbing for expansion to your heart's content;
- Rapid Mobility: Front buckle allows you to stuff the backpack and go securely without zippering the pockets;

Cons::
- Stitching: Parts of the backpack (including crucial areas - discussed later) fraying and losing structural integrity;
- Less-Than Convenient Front Pockets: Must unbuckle the front strap to access anything inside the pack;
- Lots of Straps: Expansion straps are very long and often get stuck in tight spaces when traveling;

Final Thoughts::
I'm writing this review as I'm about to retire this backpack. It has served me very well in getting all of my stuff from point A to point B at a good price, but the backpack begins to fall apart after about a year (give or take a couple of months). The shoulder straps were sturdy when I got the pack, but the stitching connecting one of the shoulder straps to the top of the pack has since given out. I have managed to fix the strap with an emergency sewing kit, but even that is going to give within the year.

This backpack has been my get-around-town / college backpack and has adequately held my workstation laptop, class notes, some textbooks, and chargers for the electronics. Filling the backpack with that much weight may have worn it down faster, which is why I would not recommend this pack for anyone who plans on using it frequently (everyday or every other day) and carrying any more than 25lbs / 11kg.

Bottom Line: Recommended For Short-Term Use (~1 Year)