This is probably not what you're looking for, as I'm assuming you're looking for a small, quick backpaking model, but I use just the cartridge from a First Need filter, gravity feed. I connect a piece of tubing between it and the spout on a flexible water jug, hang the jug from a tree, and drain the filtered water right into my canteen or other container. It puts out a lot of water with zero effort. I don't even own the pump.

Dave

A home-made gravity fed filter is described in Ray Jardine's book on lightweight backpacking- I think it's called "beyond backpacking".

I seem to recall it was pretty light but perhaps more bulky than you are looking for.

Tim H./9fingers <img src="images/graemlins/crazy.gif" alt="" />