Shellfish are mineralized shells of cirripedes (marine crustaceans). They cling to rocks, walls, ship hulls, and floating wood as well as to the bodies of marine living creatures such as algae, mollusks, turtles, and whales.
They can be used in garden or aquarium decoration. Some barnacles are collected individually and may contain glue between them, until they make up the complete piece.
Because they are all-natural pieces, the size may be 1 to 2cm larger or smaller. They may also be slightly different from the photo.