Button Top or Black Umbonium is a popular shell for crafting as they are small and relatively thin so they are easy to work with. This is the black mix (there is a natural, pink and pearlized mix also available in the store).
Please note that this is a mix of mostly black Umbonium however there still will be some natural color Umbonium in your package as they cannot be 100% sorted.
~ 1/2 C (appx. 150 shells per package)
~ 1/8" - 3/8"