The Eshopps PF-800 Hang on overflow box features a compact U-Tube Design. The PF-800 is designed for aquariums up to 125 gallons, and has a maximum flow rate of 800gph. 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, Clear U-tube syphon, nylon screw & wing nuts, black pre-filter box & 1 in. bulkhead drain.