Tux withstands chewing by my two "power chewer" Labradors, who can destroy even a large Kong!

It is a challenge to find a treat that will stuff in and take more than 10 minutes for them to get out. I have tried the Kong treats, cut to just a bit too long and wedged into the Tux. Does anyone have a recommendation? I want them to really have to work for at least 1/2 hour to get the treat!

The Zisc is really difficult for the dogs to pick up. I gave it away.

They chewed the end off of the Bumi in about 5 minutes. I am going to exchange that for another Tux.