I took a 2 liter pop bottle, marked 1/2 and 1 liter on the outside and cut the top off about an inch above the 1 liter mark. It weighs about 0.7 oz and is easy to stow. The wide open top makes for easy and complete stirring and virtually no uncontaminated water clings to this kind of plastic. It is also easy to pinch up a pouring spout so you can pour the treated water into your water bottle. The container also provides a bit more storage for camp water if you feel the need. The wide mouth Nalgene bottles I have seen are pretty heavy.