The H2Q MD VXP submersible pump with float can be used for 4 different applications. You can do this by adjusting the base. Without a base, the submersible pump is a flat piston, with the first base the pump can be used for pure water with strainer, with the second base the pump can be used for wastewater with strainer. Also, the float can be clicked up, this keeps the pump operating permanently instead of automatically. Dirt passage with the black base is 30 mm.