INOV8 Nozzles are available in several sizes - based on the desired BTUs. The standard size is a 30609-3.1 - that covers the BTU range from 125,000 to 325,000. The 30609-5 is used on the larger waste oil burners. The nozzle is an assembly that includes the brass cap, the stainless steel spinner (also called distributor) and an aluminum gasket. We also have sizes #7 and #9.