I used black salsa bowls, if you look at the
top one, i cut the legs off, the bottom one
still has the legs on it, i know it's not cannon
but i like the look. You can find them at most
kitchen supply stores, i found mine at Bed Bath
and Beyond for about $1.99 ea.
My bad i thought your were talking about
the black caps sorry, i used bottled water
bottles filled with canned foam.