Smart funnel prevents overfilling of barrels. With the funnel extension, trapped air stops the liquid from filling to the top of the barrel. It leaves just enough room to add 2 gallons more to the barrel, which is the capacity of E-Z Smart drum funnel. In order for the smart funnel to work properly, it must be removed immediately when fluid no longer flows freely. This mean the drum is full and cannot take any more fluid. Made from durable chemical-resistant polyethylene. Outside diameter: 11-3/8". Height above barrel: 11-1/2".