The product is very strong and durable, yet malleable on the outside. It zips open and close. It has a pad that comes with it inside. It is a one size fits all. Expensive, but very good quality.
I knew what I was buying & the possible limitations of the item, overall I was happy with my purchase. :)
My recommendation would be for Catteries/places that board/looked after a lot of kittens. 
My youngest cat, when she was a kitten, I got these for her. She loved them. :) I had them in corners so she could go off & be alone after playing hard, if she so chose. She used them a lot.
Now not so much, for she is bigger, & uses things she can stretch out more in, or sleep with or near me & next to her sister.
Her sister never used it because from what I could tell from watching, she found it too cramped for her body size.