This was purchased for a new home in which we'll be moving. I will update after the cats have started using it. 
We purchased two boxes. When we received them, we were happy to see that the opening was large enough to accommodate out 14lb cat (We left out the boxes for 2 days  to observe the cats). Both cats appears to like the boxes since it didn't take very long for them to jump inside. We're can't wait to replace the traditional litter boxes with these.