[Update 2010-10-28]
After about half a year, one of the shoulder straps started ripping apart at the seam, and the zipper to the front pocket had broken off. I think the high ratings for this backpack are based on early user experiences. I had initially rated the backpack 5 stars myself, but I'm downgrading the rating to 3 stars because this backpack isn't very durable. I've had JanSport backpacks that have held up to *years* of heavy use. If you're looking for something more durable, you might want to spend a little more to get a JanSport or a North Face backpack (both of which are renowned for their quality and durability).

-- Original review follows --
The backpack is perfect for school or for outdoor activities such as hiking and camping. It has plenty of pockets for putting your stuff in:

Compartments
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- 2 Side Pockets
Each of the two side pockets has an elastic band and see-through mesh netting. Each pocket is an ideal place for putting a water bottle, a pair of hiking poles, or even a tripod. I use one of the pockets for a camera tripod and the other for a water bottle when I'm out shooting.

- 3 zippered compartments
There are 3 other zippered compartments besides the main zippered compartment.

o The largest of the compartments (located in front of the backpack) has lots of pockets for putting your calculator, cell phone, stationery, etc. It has plenty of room; it will fit 3 or 4 small paperback books, just to give you a rough idea of its size. There's a hook for attaching your keychain too.

o The topmost compartment has an opening for threading the wire of a pair of headphones/earphones through so you can listen to music while the MP3 player is safely stowed away in the compartment.

Size
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The High Sierra site lists the size as follows:

Size: 19.5" x 14.5" x 8.250"
Capacity: 1949 cubic inches

It's a bit bigger than the smallest backpacks but not too big. Personally, the size of this backpack suits me *perfectly*. I wanted a backpack with plenty of room to carry the essentials but not one that is over-sized and clumsy.

Straps
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- Shoulder Straps
The shoulder straps are very comfortable even with a heavy/fully-loaded backpack. It has an elastic pocket for putting your cell phone so you always have your cell phone within easy reach.

- Bottom Straps
The bottom of the backpack has a pair of straps for strapping on additional equipment you need to bring along.

- Side straps
The side straps work in tandem with the side pockets to keep your stuff safely secured.

Quality
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The quality of this backpack is top-notch. The stitching and the materials used are very high quality. The insides are lined with nylon (makes backpack water-resistant).

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I absolutely love the High Sierra Loop Backpack. It is just the right size for me, it has plenty of pockets, and its quality is superb. If you're looking for a medium-sized backpack, this one is definitely worth consideration.