These plates can go under  any mug to prevent spilling. When you carry a mug with this plate you are using it as a saucer. It does not matter what size the bottom of the mug is because the rounded shape keeps the mug from sliding and spilling. This for me means I now can use all of my mugs or cups that do not have a saucer with them. That is why I bought them and I am so happy to discover this. I hope you can use this information .