Be sure and call them if you need info. I know some people said they had issues but I have called several times when I was getting my first rack and they answered everytime and answered my questions. My Herp Buddy has as stack of the 421's with the heat panels and they are great. He also has a stack of the 6' cages and has never had any issues with either. The way they are built inside makes them very easy to clean. I personally have not seen the AP cages in person so I cannot speak for them.