From our Lava Rock Collection, each rock measures on average 1/2" - 1" and is used as an accessory to our Fire Glass or fire pit. We recommend using Lava rock as a filler if you have a deep fireplace or firepit. For a complete design, add Fire Glass on top to cover the fire rock thoroughly so it will not be detectable. We currently offer lava rock in 10 lb. bags, which is equal size to 20 lbs. of Fire Glass. Because lava rock is economical, it is the perfect choice as the first filler that goes into a very large and/or dept fire feature to cover up the gas piping and tubes. Once the lava rock is spread the way you want it, add a layer of fire glass to create a truly astonishing design that will instantly become the focal point of your home or yard. We sift, sort and pack all of our lava rock by hand. This way we can guarantee that they are top quality, can be used in a firepit and have no left-over gas pockets that could burst. For optimal results, our recommendation is to pour a minimum of two inches of lava rock over the firepit burner, which allows the gas to filter evenly through the lava rock media. Remember to cover your firepit when not in use and do not use the fire feature when wet.