I have two of these Camelbaks. I have an older model and a newer model for comparison. The older model first - the hydration pouch itself holds the same amount but is all one shape, and the drinking tube and mouth piece are not as big. the compartments themselves inside the pack are very narrow, and once the bladder is full, it is hard to access anything inside of them except the very outside pouch. I did like it when I bought it but after using it a a bunch developed a dislike to these things. The NEWer model - I love it. The bladder is designed diff, the bottom being more narrow than the top, still holding the same amount, but the water does not sit at the bottom as the level get lower, keeping the bladder from bulging out (prev error fixed!. Bc of this the compartments are all easily to access, even when water is completely full. Additionally, these compartments are more thought out, and seem a little roomier. The tube on the bladder and mouth piece are also bigger, and allow more water flow, and the top on the bladder is a screw on vs the weird lock in function before - MUCH MUCH easier. The back on the newer is also slight arched to allow more air flow. Would reccom this to anyone who needs lots of water, and doesn't need a whole lot of space.