We use the Petmate Litter Locker Plus, which allows you to scoop and store easily and contains the odor. About once a week, we remove the used portion of the bag. We buy refills (the continous plastic bag insert) about every two months. I might also add that a really nice scoop is included with it, and the box has a place to store the scoop. It is really great if you need someone to petsit, because it is so easy to use. I absolutely love it, and would highly recommend it.