These natural porous calcium carbonate rocks are sliced on two sides to create ledges, platforms, and caves, and are perfect for fragging corals of all sizes. Flatz can also be used to design interesting substructures, rock footers, and sandless substrate beds by tiling in across the tank bottom. Each box contains a variety of sizes from about 2 inches to upwards of 10 inches. LifeRock Flatz have coralline algae coloration.