Hearth Products Controls (HPC Ceramic Fiber River Rock (FPR84MC), 1/2 Cubic Foot, Multicolor Synthetic fire media for use with gas fire pit or fireplace Multicolored black, gray, red ceramic fiber river rocks are safe to use at high temps 1/2 cubic foot bag Rock pieces vary from 2.5 to 4.5 inches in size Perfect for use with a gas log set