A bottom drain and an air diffuser built into one unit!  The circulation created by the air diffuser will increase the amount of debris removed by the bottom drain and will increase oxygen levels in the pond.  Bottom drain base has six stainless screws and two rubber gaskets for a positive seal when penetrating liner!  Connects to 3" PVC pipe and fittings.  Air diffuser is set up for 1/2" tubing, recommended air flow of 1/2 to 2 CFM.