Is it a 10 litre or 2.2 Gallon emergency hydration pouch, perhaps its Compression Dry bag to keep your sleeping bag and clothing dry in wet weather or perhaps its a Solar Shower, well its all three, the Ortlieb Water Sack 10 Litre (Black).



This was just what I was looking for. A lightweight and useful bit of kit with multiple uses. Oh and it can be used in conjunction with a Katadyn Siphon filter for a large capacity gravity feed water filter and with the wide roll top closure it is easy to clean the inside.

http://www.ortliebusa.com/CartGenie/prod-68.htm

http://www.ortlieb.com/_pdf_en/watersack.pdf