These lava rocks are gas grill replacements, and should only be used on gas grills and charbroilers that are designed to use lava rocks. Clean the rock grate and firebox after removing old lava rocks. Place the new lava rocks on in one layer, close the grill and burn grill on "High" for fifteen minutes, to allow the rocks to season. One bag covers approximately 300 square inches. Sold in 7lb. bag.