Abalone shells: 2-3" sizes may vary.
A gift from the sea and, thus, symbolically represent the water element while the unlit herbs represent earth, the lit herb represents fire and the smoke represents air.
Abalone shells are a very popular material for use as a smudging bowl. But be careful not to handle the shell midway, since heat also transfers to the shell. Abalone shells, being shells, are not bowls, so they sometimes have holes in them