"I hated this cage for the longest time after reading all the reviews. However I have 4 female rats and I was in desperate need of a larger cage, and this is all I could afford.
I must say I'm impressed. It's not nearly as bad as I had first thought. Yes, the shelves are saggy. Yes, some of the bars are week. And yes, the slide, tunnel, and ramp are made of cheap plastic. These are all just minor imperfections though. The construction of the cage is not the cause for saggy shelves and weak bars, but it's the size of the cage that's the problem. The larger something is, the more unstable it's going to be.
As for the bar spacing, young rats WILL get out. I have 2 very young girls, 1 adult girl who's just smaller than most others, and another adult girl who's a typical size. My two youngest are able to fit through some spaces, but after the first day they stopped trying to get out. I think this cage would be perfectly fine for full grown rats. However I cannot imagine keep a ferret in this cage. The weight of a ferret would be way too much for the shelves and slide.
Overall, I'm glad I decided to purchase this cage. However I still don't think I'd recommend this to anyone. I'd much prefer the "Super Pet My First Home For Exotics" It's slightly smaller but quite a bit more sturdy."