I have tried other automatic litter boxes, and none of them compare to the Scoop Free boxes.  My cats have done their best to try and break the boxes by standing on the rake while it is moving, but have not succeeded.  The boxes have wonderful removable trays that make it easy to replace litter without scooping or touching the litter. We have 3 cats, and 3 Scoop Free boxes. I have bought additional units for family members because I love ours so much.  I highly recommend this self-cleaning litter box!