This was a confusing set up since the pieces are not labeled and it was a struggle putting the stairs and shelves since it's a tight space. Overall, my 4 rats love this cage and are happy! Baby rats may be able to go through the bottom sliding compartment. So far so good, other than a manufacture issue so I could not screw in one bolt and the hanging hammock is cheap and uncomfortable for them. Update few months later: The bottom tray cracked and its super hard to clean. I wish the top and sides would open, it would be easier to add enrichment and do daily wipe downs. Cheap Cage.