These fist-sized pieces of LifeRock each contain a single through hole perfectly sized for receiving frag plugs. Fraggerz are the easy way to isolate individual corals and prevent unwanted spreading from rock to rock. These beautiful rocks make corals easy to place by holding frags securely (hides ugly plugs, too) and allow easy re-location around the aquarium as corals grow. Fraggerz can also be easily placed on existing rock structures or left free-standing in the substrate.