For some reason, my cat has never been too happy with these cubes. I'm not sure why... There's no problem I can see, but when they are open and out, he hardly ever uses them. We've had them out in different rooms, in different ways... Nothing. He's spent maybe half an hour in them, and we've had them for over a year now.
He's used other cubes and tunnels, but these just don't impress him.
They're otherwise a decent product... Easy to clean, fold up small for storage, durable. There is a dangly toy inside (though my cat has NEVER even glanced at it!). But if the cat isn't pleased, none of that matters much!
There are other products on the market (including other "pieces" from this maker) that I'd suggest trying out. Skip the cubes and go for the more interesting play-gyms.
I even tried using them in our small-animal "playpens". Funny enough, they ignore them too (and not other products similar)!