This is the Hanging Energy Retention Disk / Target for Clean Burn furnace models CB 1500 CB 1750, CB 2500, CB 3250, CB 3500, and CB 5000. This is the latest design from Clean Burn replacing previous Ceramic Targets and Stainless Steel Targets. This target hangs on a hook in the back of your heat exchanger. It is made from a silica refractory material. It looks similar to an egg carton but much more durable and heat resistant.