I have the Katadyn Combi and it takes a while to get used to. You have to pump the handle to filter the water. You may think this takes too long at first. It takes a few minutes to pump enough water to fill a quart container. The bottom will attach directly to a Nalgene bottle, so it won't spill during filling. It has an extension hose for filtering shallow pools of water. For maintenance, you have to unscrew the bottom of the case and scrub the ceramic filter, which clogs depending on the purity of the water. The casing is made of hard plastic and needs to be packed carefully, because the plastic will crack in certain instances. My son cracked the housing, when he packed it in an outside pocket and fell on a rocky trail. I think it is good for 10,000 gallons. You have to buy charcoal packets, which don't last as long as the ceramic filter, but after I use the Combi, I dry out the charcoal and reseal it in an airtight container, until I need it again. And lastly, the German Army uses it, so it has to be good.