Jackson, my 16lb'er does well with the Kong Classic Medium (the red one) but he could also use the Large if we wanted.
I usually put some kibble in there and then seal it with wet food, then put it in the freezer. He enjoys it.
I used to also put plain non fat frozen yogurt in there and freeze it, but he started not caring for it, and then he'd only lick the top off and I'd have to clean out the rest
so I stopped doing yogurt...
I dogsit and one of the dogs always has a Kong stuffed with kibble and peanut butter -- it's organic no fat unsalted PB though.
