Here are some possibilities:
* Earth's crust: The Earth's crust is the outermost solid layer of the Earth. Its thickness varies greatly, from about 3-5 km under the oceans (oceanic crust) to about 35-70 km under the continents (continental crust).
* The crust of a bread: The crust of a bread can vary in thickness depending on the recipe and baking method.
* The crust of a pie: The crust of a pie can also vary in thickness depending on the recipe.
Please provide more context so I can answer your question accurately.
