Cars like boxes and this one is the perfect size with the purrfect inserts. The base is about 16” x 13 and 3.5” deep. There are 3 high quality, very dense corrugated cardboard inserts included, and these are each about 1” deep. Take out the 2 extra so only one is the bottom and your cat cannot resist sitting in this box. I didn’t have to sprinkle catnip. My cat got in it as soon as I set it on the floor. I did put a little nip on it later just for their pleasure. The scratching cardboard is such high quality that after 2 weeks and multiple cats using it for a bed and scratching post, there’s hardly a mark on it and no bits of cardboard laying around. In fact, I just use a microfiber cloth or hand vac to get the hairs off it. This set is 10 times better than a similar item I purchased for twice the price at the pet price. It’s going to last a long time ( you can flip the inserts when one side is worn out). I’m not sure if refills are available however if not, I’d just as soon buy another set. It’s that good and cat approved.