I just kind of make up fillings lol PB or cheez whiz or both, with plain yogurt, and treats. or sometimes I will roll baby carrots or apple in olive oil and stuff the kong with it, and sometimes hotdogs jamed in it. just things like that, and sometimes I freeze it and sometimes I dont. but I tend to be rather creative when suffing kongs because my dogs have them cleaned out in minuts, or if its not something really packed in then it takes them all of 60 seconds to unstuff it. I just look around add cereal, and whatever I find that will make it tasty and difficult. I have never bought kong stuffin, I dont really see the point lol