American Fire Products LAVAST-M-20 20 lbs. Medium (1" - 2") Natural Gray Tumbled Lava Stones have a modern, classy look that adds a warm rustic elegance to any fire feature. These stones are naturally formed & then put through a smoothing process giving them their uniform shape. Because they are volcanic, they can withstand the most extreme temperatures without sustaining any damage or crumbling, making them a cost-effective, long-lasting & beautiful addition to your fire pit, fire bowl & indoor or outdoor fireplace. Lava stones offer durability and provide a low maintenance unique natural element that looks great as part of your indoor or outdoor décor.