What size Kong do you have for your dog? I think right now I have the Small Medium (I bought it when my dog was still a puppy) but now he's full grown (at least I hope he's done growing!) He's a Chocolate lab mix, and he's just over a year old, and about 85-90 lbs. Think I should move up to the Large/X-Large size?

Also what do you fill it with? I would love something that wouldn't be horribly messy and get on the carpet (that's why I've been sticking to peanut butter)