You have to get a little creative with stuffing it. I use some cheese spread to coat the inside, because our dogs don't like peanut butter, and then stuff it with boiled chicken. It keeps them busy long enough to distract them from the initial distress of 'oh no people have gone out without us!' so it is a really good way of dealing with mild separation anxiety. They love playing chase with each other with the kongs, too. We have a kong extreme as well, but for moderate chewers, classic is strong enough, I think.