We rescued 3 kittens in late October when it started dipping below freezing and mama cat was nowhere to be found. As we have an adult cat of our own, we needed to isolate and quarantine them separately from her.
This enclosure is compatible with a ton of attachments from the same company to build a custom enclosure that is suitable for your space and for your cats. We did NOT use it outdoors - this was used indoors in a basement and was able to keep the kittens contained from about 8-10 weeks old to about 16 weeks old without issue.
They loved being able to climb to the platforms. Funnily enough, I couldn't find one of them once - because he had climbed all the way to the top of the 'enclosed' platform and wedged himself on top of it. I just hadn't thought to look for him there, but he was having a great time!
I'd totally repurchase if I needed more space for littles, and I'd definitely recommend to friends or family who are rescuing.