This is a test of commonsense. Complete the next sentence:

How to make reed diffusers
Find a container with a narrow opening.
Begin assembling your reed diffuser by finding a suitable base container for the reeds. Look for a container that is about five to ten inches tall with a small opening made of ceramic, glass, stainless steel, earthenware or wood.
Do not use a plastic container, as essential oils can react with plastic. A small opening at the top of the container ensures that minimal evaporation occurs.