Max. Flow Rate: 600 gphOutflow Size: 1" bulkheadBulkhead Width: 8"Needs 4.5 inches between back of tank and wallA built-in overflow is the most efficient method of draining aquarium water to a filter. If your aquarium does not have built-in overflow, CPR Aquatics Siphon Overflows are the best means for getting water from an aquarium to a filter system without expensive modifications to the tank. They quietly skim up to six times more water than units with tubes.We highly recommend using the Aqua Lifter pump with your CPR Overflow to maintain siphon. You may also want to look at our Wet Dry Filter page where we have recommended packages including the Overflow Box, Aqua Lifter pump, return pump, Wet Dry Filter and plumbing.The advantages of CPR Aquatics Siphon Overflows include:Adjustable water level allows you to easily change the level in your tankBlack top reduces algae growthPlastic screen to prevent fish lossQuiet operation