Keyhole Limpets move about the reef, substrate and even glass. Their body is protected by a cone-like shell that has a small hole at the apex or top. When extended, some display a delicate lace-like fringe or skirt. I have had a few of these over the years, and usually they are about .75" to 1.5" in size. Many babies about 1/8" appear in the sump, refugium and plumbing. Reef-safe.