GUU is a button mushroom with little slit pockets to hold rewards. The round, unstable bottom adds on to the challenge and they are just perfect to play fetch with!Longer pieces of treats work best for the GUU. We do not recommended using kibbles or pieces that are too small. If the treat is completely inside the pockets, your pet might get frustrated (since they have paws, not fingers)! Pockets can be pulled out for washing. Kitty owners can insert catnip in the pockets too.Small: 5", suggested for breeds such as chihuahua, italian greyhound or catsMedium: 6", suggested for breeds such as shiba, corgi or poodles Each pup plays differently and we recommend you to keep a close watch particularly during the first time a new play object is introduced. No toy is completely indestructible, so please supervise the play to ensure safety if you know your pup is not gentle with toys.