not sure how well it would work for a multi-cat household but it works great for one cat. If you have a whole bunch of cats I imagine you'd have to dump it more often. The bottom half of it is where all the litter falls so when that part of the bag gets full, you can't slide the trapdoor shut any more.

here's an x-ray view for those of you who are curious how it works: the collection bag is over 10 feet long and wadded up around the rim of the refill. Just pull down about a foot (enough to reach the bottom of the collection bin) and tie a knot in it. Drop your clumps in the top and open the trapdoor to let them fall into the bottom. When the trapdoor shuts it holds the bag shut and seals out the odors. When the bottom part is full, there is a blade inside so you can pull down more of the bag and cut off enough extra to tie it up for disposal. Then just pull more of the bag down, tie a new knot and start over!