This is a hydration pouch that is designed for day hiking. Inside you have a bladder in a back pouch that is filled with water. You also have a hose connected to the bladder that follows one of the two shoulder straps. This means you have easy access to your water source. To drink you just need to bite down on the bite valve and suck. Since gravity is working for you it does not require much sucking to acquire the water until it gets low. There is also an on/off valve that needs to be turned on so the water can flow.
In addition this pack has several pouches for extra stuff. It is a great pack for a nice day hike.

Back design
The back portion is made of three pieces of padding. Two pads for your shoulder and another pad for your lower back. The pads are covered with a mesh that helps with airflow. Between the pads there is a space of about 1 inch. It is in the shape of an upside down Y and is designed to increase airflow.

The shoulder, harness, and hip belt design
The shoulder is a very mildly curved S design. It ends up being a fairly comfortable design. The straps are padded, about 2 inches wide, and it is also lined with the same mesh as the back pads. There is also the typical middle strap that holds the shoulder straps in place.
The belt is pretty basic. It is mainly designed to keep the bottom of the pack from flopping around. It is not designed to support the weight of the pack like a normal backpacking hip belt would.
The harness system is pretty typical. You have two shoulder straps. On the shoulder strap you have a clip belt that secures the two should straps together.
In addition you do have a hip belt of sorts. For me this belt rides about 3 inches above my hips. The only reason you will use it is if you run or bike, but because of the size/weight of this pack I do not recommend running, CamelBak has better hydration pouches for those type of activities. Get a smaller pack like the Lobo. I only hike with mine so I removed the belt from both hydration backpacks. My mother-in-law has chosen to keep hers attached.

Are the shoulder straps universal or gender specific.
Most packs are universal or designed for men. The Blowfish, the Lobo, Peak Bagger, and this pack fit that category. If you are the better looking of the two sexes then I recommend you buy the CamelBak that is specifically designed for women. There are a couple of CamelBaks out there designed for the feminine gender.
I recommend the female designed pack to my mother-in-law. After she tried it on at REI she did not like it, instead she went with a regular design because it fit her body better. As always, try before you buy, and don’t believe everything you read.

Main features
Carrying loop
Compression straps
2 elastic side cup holders,
Sipper straps
Exterior elastic band gear holder.
Hydrolock.

How to fill it.
The bladder fits snugly in the back pouch of the backpack. You unzip the back pouch to gain access. You simply unscrew the top of the bladder, hold the backpack/bladder underneath the water source, fill it up, and screw the cap back on the cap. The cap is almost 4 inches in diameter so it is easy to fill.
Unlike my Lobo, you do not have the easy fill feature. Here you have to unzip the bladder compartment and partially remove the bladder so it can be filled. This does not have the easy fill feature like in the Lobo.

The compartments
The outer compartment is designed for your lunch or smaller pieces of gear. The compartment is separated by a nylon partition. Attached to that partition are 2 mesh pockets able to hold keys or a small wallet. The two pockets are about 7 inches deep and about 6 inches wide. Enough for lunch and a snack.
The main compartment is about 20 inches deep and about 12 inches wide. There are no small pouches, just one deep big pocket (approximately 20x12x5 inches)

My opinion on the bite valve.
When comparing the bite valves I prefer the MSR bite valve over this one. I think the bite valve is comparable to my Platypus valve. Ultimately I do not have a problem with it, I just wish the flow rate were higher.

Does the on/off valve work?
It does. At first I thought it was just a gimmick. But on one trip I had a stack of papers I was reading that found their way underneath my CamelBak backpacks. I did not lock the bite valve unit and the weight of the backpacks on the bit valve caused valve to open up. All of my papers were ruined. So I highly recommend you use the on/off valve when you are transporting these backpacks.

Does this have an antibacterial bladder?
The new versions do. Just keep in mind that as of this writing, some stores are still selling the old bladder. If you do not see a tag that says it is an antibacterial bladder than do not buy it. This new bladder material is well worth it.

Does the antibacterial bladder material really work?
I deliberately left water in both of my CamelBak’s for several weeks. My Lobo, without the antibacterial bladder, had an off taste to it. This would be a bacteria or fungus growth. My Blowfish with the antibacterial pouch did not have the same off taste and the water (which is bottled) tasted just like it did when I went hiking several weeks prior. The antibacterial material works, which is why I wouldn’t buy another bladder without it.

Why should you get one?
I highly recommend a hydration system in general because it allows you to drink on the move. This helps a hiker stay hydrated better. Normally when I hike I usually don’t stop to drink until I am really thirsty. By that time the first signs of dehydration start to show and my performance suffers. But by having a hose near your mouth you are constantly reminded that you have a water source with you.

This pack in particular is good if you do day hiking. You have plenty of room for food and gear for a full day hike.

Which CamelBak is right for you?
I would recommend you go to http://www.camelbak.com/rec/products.cfm and use their program to select the pack you think you will want. This can help you narrow down your choices to a couple of models. But I still recommend that you go to a store and check it out for yourself instead of buying it online sight unseen.
Also Platypus, Jansport, and others have started putting out a backpack/bladder combo of their own. I have not taken a close look at these but it does provide you with other options.

Who is this for?
This would be for someone that takes day hikes and likes to bring their lunch with them. There is plenty of room for other stuff but I would not put more than 25 pounds in this pack because it does not have a supportive hip belt. If you need to carry more gear then I recommend getting a backpack like the Northface Terra 40 There is also plenty of room for a camera or other gear one may need. Just not enough room for an overnight stay or a daylong hike in 100+ degree weather. But the main reason I recommend this type of backpack is that the hip belt is designed to support most of the weight. It makes hiking a lot move enjoyable.

Weight and dimensions
Bladder Capacity: 100 oz / 3 liters
Dimensions: 20.5 in x 12 in x 7.5 in (521 mm x 305 mm x 191 mm)
Cargo: 1526 cu in (25.00 L)
Weight: filled 8.40 lbs (3.81 kg) empty 1.80 lbs (.82 kg)
(info taken from CamelBak.com)

How to clean it
Since it is made from an antibacterial material so you should not have problems with off tasting water. But if somehow you do get an infection (which is common with older bladders) then one trick is to make a low concentration of water and bleach. About a tablespoon per gallon of water for 15 minutes should do it. Bleach is inexpensive but can damage your bladder if you leave the bleach mixture in the pouch for a prolonged period of time or if the concentration level is too high. And if not properly washed out then you will have a bleach taste in your water.
If you feel uncomfortable using bleach then go to REI and get their special bladder cleaner and follow the directions. It will be more expensive but safer to use (or so they say.) Several manufactures make cleaning agents including CamelBak.

Accessories
-Ice Tubes- This is a deep ice cube tray that makes long ice cubes.
-CamelBak cleaning tablets- These are tables that will kill the bacteria that try to live on your plastic. If you do not want to use chlorine bleach then these tablets are a good alternative.
-CamelBak cleaning kit- Comes with all the equipment you need to clean out your bladder.
-CamelBak hanging rack- Helps your bladder dry out.
-Clip- used to clip the bit valve to your strap or clothing.
-Hose insulator- Keeps the water in the hose from heating up or cooling down. It is actually something I will get.
-Rain cover-
-Filter-
-Cell phone holster-
-Bite valve cover-
-Ergo Angle-

Summary:
This is another great hydration backpack from CamelBak. It allows you to drink water while you are still walking or biking. The pack is comfortable and well designed. It also has plenty of room for a full day of hiking, unless you like to take your SLR and 20 different lenses. I highly recommend this pack for the typical hiker. If you bike or run professionally then you may want to look at a lighter/smaller model.

Other outdoor products you might be interested in.
CamelBak Hydrolock
CamelBak Lobo
MSR hydration system
MSR dromedary bag
Camelbak Rim Runner 2010 version. Very much improved.

Recommended: Yes