Rating: 5 / 5
I find that I am more consistent in drinking when I use a hydration system. The BigZip is lighter than most other hydration systems, while still having a large opening which makes filling it easier. The original version of the "zip" failed me twice (accidentally opening). I have been using the Zip II since early 2008 without a single problem. The new zip top is much easier and more reliable to close than the first generation platypus zip lock containers. The quick release value works well making it possible for me quick switch from hydration bladder to the "dirty" bag in a gravity filter system which I am using a combination of filtering and chemicals. The "on/off" lock on the bite value has saved me a number of times. With either models I would sometimes lean the pack against the bite value which would then leak water. This doesn't happen now that I can twist the value to an off position.