More than just a water sack an extremely handy and useful piece of kit to have in you collectionas a water sack this has all the features that you could look for a wide opening to fill it up which is closed off with a reliable roll top closure which then doubles up as a handle the valve has a metering control on it to regulate flow and is protected with a dust cap it can also be connected to a shower valve drinking hose or water purification filters eg general ecology sigg msra grea