CPR CS50 Aquarium Overflow BoxA 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 Continuous Siphon Overflows/Prefilters 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.The advantages of CPR Continuous Siphon Overflows/Prefilters include:Adjustable water level allows you toeasily change the level in your tank.Black top reduces algae growth.Quiet operation.CS Overflows feature a grated inlet.Specifications:Model: CS50Flow Rate: 300gphOutflow Size:3/4″ BulkheadProduct code: 26Item No. OF-CPR-CS50