Do you mean the Katadyn Base Camp? I use one a lot for backpacking and it works great. The actual filter is the same as in the pump version, it is attached to the bottom of the bag so gravity does the work instead of having to pump. It is heavier overall but really convenient if you have a decent size stream to fill the bag then just hang it up and put the hose into your water bladder. Come back a few minutes later and your water bladder is full of clean water.
Not sure if the Base Camp comes with it or if you have to add it but Katadyn has quick detaches for the hoses on the Base Camp and your water bladder hose. Just disconnect the bite valve and plug in the hose from the base camp and you can refill your water bladder without taking it out of your pack.
