Keegan has a King size Kong that I had originally bought for Shaianne. Neither one of them pay/paid attention to them unless they have something in them. I fill it now with either watered down dog food that has been frozen in them. Or I fill it with Frozen Bil Jac which she loves. Keegan had a very small one that way she would still stay busy, but wasn't getting all the extra calories of it from the big one, and I think she had that almost a year and half and finally had to pitch it b/c it was separating around the middle. So I got her a medium/large one.
When I first bought the King Kong, I bought 2 and a guy from work bought the other one from me. His dog LOVES it. Plays with it all the time.
Keegan also has 2 of the biscuit balls. A small one and a huge one.
She has a rubber football shaped biscuit thing. It isn't a kong but she won't touch it even if there is a biscuit in it. She must not like the smell or taste of it.

Nicole,
Is what I do to clean mine, is soak them in hot soapy water for a while and believe it or not, soaking them in denture cleaner also helps. I use those tablets to clean a lot of stuff. Then clean it out with a baby bottle brush. It works great for the big one, and it also worked for the small one I had.