Complete wet/dry filter combos are exactly what your tank is looking for enhanced biological filtration and simple setup. Each complete biological filtration system includes an overflow box, bio balls, a drip tray & cover, egg crate, filter pad, return valve, clear vinyl tubing, a 1 in. bulkhead and 3 ft. of 1 in. flex hose. The simplest choice for advanced aquarium biological filtration with wet/dry filters.Advanced U-tube style compact overflow boxes are designed to fit between your tank and your wall to maximize space usage in your aquarium setup. With only 3 in. required between your tank and your wall, these boxes are excellent for optimizing space. Each box includes everything required to attach it to your system and comes with a foam prefilter. It's always a good idea to achieve greater volume in your aquarium; do it the easy way with one of these overflow boxes. Each unit includes a U-tube tube, cylinder foam, nylon screw & wing nuts, black pre-filter box & 1 in. bulkhead.