Looks like just another water carrier, huh? Not so… This little dude carries 2 liters and packs in at only 1.2 oz.. Significantly lighter than that Nalgene bag or worse the big plastic bottles.
We use this to carry spare water if we need it, and to treat our water. As we use a chemical treatment for purification, we fill this bag up in a lake or stream, drop a few MicroPUR tabs in, wait 30 minutes and are good to go.
It can also be filled with air at night and double as a pillow, and on particularly cold nights, you can heat up some water on the stove, pour it back into this bag and take it to bed as a hot water bottle (Nice tip from Tim)
I also pack a platypatch in my first aid kit, just incase it ever springs a leak. Hasn't so far…
Water container from REI for $6.95.