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" 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. Click here for directions on how to install your overflow filter system.