The Eshopps WD-300CS wet/dry filter is a complete filtration package; including a classic Wet/Dry type fitler system; and a Hang-On Overflow box; for aquariums up to 300 gallons. This combination is ideal for providing enhanced biological filtration for your freshwater or marine fish aquarium. The WD-300CS uses replaceable felt filter pads; which provide mechanical filtration that removes uneaten food and fish waste. Dual Bio-Ball chambers provide biological filtration by giving large surface area for the growth of the beneficial biological bacteria that helps quickly break down ammonia and nitrite. For aquariums that do not have a drilled overflow system; the included compact dual U-tube style overflow box allows for installation on virtually any aquarium. The Hang-On overflow is only 4" wide; minimizing the space required between your tank and wall. The system includes a two 3' drain lines and a length of vinyl tubing with a valve for return lines; all you need to supply is an appropriate return pump to get up and running. Separate chamber provides space to house a return pump (not included). Filter measures 36 in. x 14 in. x 16 in. and is rated for 200-300 gallon aquariums.