One of the problems with this type of litter box is that rabbits like to chew on the removable lip that comes with the litter box. I don't know why the manufacturer even bothered to put it on. I (or the rabbit) took all of them off of my litter boxes.
The small wire grate is not very durable either. I purchased several litter boxes over a period of time and most of the wire grates failed within 2 months of use. These litter boxes do work great for kits and young juniors, though. I usually leave these in my weaning pens.