We are second time cat genie owners. We have found this to be the most sanitary option for our home. We used our original one with one cat for about 4 years before it died. We reordered the main unit, but not the dome and sidewalls because we already had them. I highly recommend the dome and sidewalls, but not the door, if you have a bigger cat. Our cat is 15 lbs and she will climb in and turn around with her head sticking out the hole. Having the flap there would be a flap in her face. I also highly recommend trying both types of cartridges, scent free and fresh scent to see which you prefer. Even after 5 years of cat genie use, we still don't prefer either one. My husband thinks that fresh scent doesn't smell so fresh, but that it is better than scent free. Scent free is better when all of the waste has been scooped up, but if the scooper missed any of it or it didn't get washed away (which sometimes happens with our cat) then you end up with the waste getting baked by the drier and no "fresh scent"