Rasmussen 20" Calico Mix Alterna Ventless FireStones Single Sided - AFS20-CX combines a variety of natural hues to bring a unique, multi-tonal style to your ventless fireplace. Crafted from durable ceramic-bonded refractory material, these firestones offer high heat resistance and a distinct look without cracking or popping. Designed to elegantly conceal burners, this calico mix set is exclusively compatible with Rasmussen Alterna Vent-Free FireStones Burners (sold separately), adding a warm, transitional touch to any space.