The Katadyn BeFree filter is an awesome solution for back-country water filtration. The BeFree consists of a collapsible water bladder that is easy to fill in any stream or lake, and filter top used for drinking. Just apply a little pressure to the bladder to drink clean, safe water. One of the nice aspects of this product is that if the filter gets clogged with debris from your water source, the EZ Clean membrane is very straightforward to flush. Just attach the filter to a partially filled water bladder and shake, or swish the filter in a stream or lake. The empty bladder compresses down so it doesn't take up room when you're not using it. The filter comes with a 0.6L, 1.0L, or 3.0L bladder.