I have a 44 pound Belgian Malinois and Lab Mix and Pekingese and Borser Collie Mix at 22 pounds. At the time I ordered this box I had ordered the small size thinking my then 6 month old BM & L Mix would do no damage. I was wrong....he did. So I ordered a medium box and although we got alot of the same toys just in medium we stick to the size now. Both my dogs adore this toy and as soon as one puts it down the other one snatches it. After a few months they haven't gotten to far into it. Does need to be sanded down though which is why it's currently put up.