For all types of freshwater tanks and for saltwater fish only tanks tanks up to 125 gallonsCapacity: 4 gallonsDimensions: 21" length x 10" width x 15.5" heightInternal Sump 9-1/4" length X 8-3/4" widthIncludes Bio Bale biological media1" bulkhead inlet / No outlet bulkheadFor a complete filtration system including an CPR overflow box, plumbing, hoses, siphon pump and return pump (see picture in new window), just order the following products along with your CPR CR900 Wet Dry Filter:CPR Wet Dry Connection Hose, 4 foot CPR CS90 Siphon Overflow Aqua Lifter Water & Air PumpPython 10 ft, Clear, Ozone Resistant Airline Tubing (for Aqua Lifter Pump) Rio Plus 2100 Pump (UL Listed) Inland Seas Over the Back ReturnCPR Wet Dry Filters are designed for long term reliability and ease of maintenance. These filters incorporate superior design features, such as:Simple installation and operationCompact size to easily fit under your aquarium standExcellent craftsmanship, all edges flame polishedEfficient drip plate or drip lid dispersalSpecially designed vented lids allow for proper gas exchange, and do not warpIncludes Bio Bale biological filter mediaWet Dry filters are recommended for all types of freshwater tanks and for saltwater fish only tanks. Wet Dry filters work by mixing air and water mix as the water from the overflow box trickles over an exposed filter media such as Bio Bale. Biological filtration and gas exchange occur as the water flows in a thin layer over the media surface. The Bio Bale media provides optimum growing conditions for bacteria, which oxidize nitrite and toxic ammonia. The rapid oxidation of ammonia and nitrite helps to maintain a stress free environment for aquatic life.