There are two sizes of shoes available. There are small shoes and medium shoes. Can’t decide which size you need? There really isn’t an easy guide for this. I have found in the past that I’ve just always had both sizes on hand. When I asked the Shoe Baroness about this, this is what she said

“Here is the story on the PEZ shoe sizes. Not all PEZ stems are the same size. It's like going to the shoe store; you need to fit the shoes on your individual PEZ. There is a minute difference between the length and width of the Small and Medium Pez shoe sold by Imelda's Shoe Factory. An older N/F PEZ will probably require a smaller shoe than a newer N/F PEZ. But, as with all things Pez, everything is relative and there is no hard and fast rule. The best prediction I can make on the best fit for PEZ shoes is some shoes will fit some stems and some shoes will fit others . My collection has lots of both sizes, including some shoes that have been trimmed out to be just a tiny bit bigger. There once was a shoe that you will hear referred to as a "large" Pez shoe. That shoe came from the first run through our mold, but cannot be reproduced because modifications were made to the mold after these shoes were made.”