The return pump is by far the most important piece of equipment on your aquarium. It circulates the water which is basically the life-blood of a tank. Via its AquaBus port the COR can be easily connected to the Apex.The COR-20 is a variable speed, brushless, DC-driven centrifugal water pump designed specifically for aquariums to be intelligent, energy-efficient, unbelievably quiet, and incredibly powerful for its size. One COR-20 pump provides enough flow for aquariums up to 180 gallons! For larger systems two COR-20 systems can be used.Included is a 1.25″ BSPP -> 1.25″ Slip PVC Unions so that you get the optimal flow from your COR-20. Plumb your system with 1.25″ and see what this pump can really do! The COR-20 is very energy efficient, it uses less than 90W of power.INCLUDES COR Pump COR-20 Pump Driver 100W 24VDC Power Supply Power Cord 1.25in. PVC Union (Slip->BSPP) 1.0in. Slip Fitting 0.75in. Slip Fitting 3-foot AquaBus Cable PHYSICAL DIMENSIONSPUMP: 3.875”W xv4.875”H x 6.250”DDRIVER: 3″W x 4″H x 1″D