The Propane Valve adapter allows you to use any of the smaller propane bottles, especially the 1lb size. At full blast, each 1lb propane bottle should last over 1 hour. However, with a low flame, your bottle should last several hours. Made from solid brass, this will adapt your hose/regulator assembly so that you can use the smaller bottles. It is small, easily stored inside the Volcano case, so you can have it with you always. Note that a normal 20lb tank -at wide open - should last about 22 hours, much longer if you are using a low flame.
The middle grill is a great addition to your charcoal Volcano cooking. With the middle grill you can do a wide variety of things. You can use it as a second cooking surface if you are using charcoal, doubling your cooking surface to 288 square inches. If you want to bake with the middle grill, you can (in conjunction with the Volcano Lid) use a normal bread pan to bake a loaf of bread.