The Eshopps PF-1000 Hang on overflow box features a compact Dual U-Tube Design. The PF-1000 is designed for aquariums up to 150 gallons; and has a maximum flow rate of 900gph. At only 3" wide; minimal space is required between your tank and wall; these boxes are excellent for optimizing space. The interior black acrylic overflow box is adjustable so you can set the water level in the aquarium where you want it; and efficiently pulls water of the surface to keep the surface clean. Each box includes everything required to install on your aquarium and includes; Foam prefilter; Two Clear U-tube syphons; nylon screw & wing nuts; black pre-filter box & Two 1 in. bulkhead drains.