This is the Poly-Mart 1" Tank Plug.
An outlet Tank Plug is included with every tank and are available in various sizes including 3/4", 1", 1 1/2", 2". The plug may or may not be used in your application depending on whether or not you choose to use and Ball Valve of some sort on your Outlet Fitting. If the included plug is used in your application, remember to use plumbers tape or sealant on threads to create a water or liquid tight seal before filling.Ships FREE with the purchase of any Poly-Mart Tank!!