Feature: 1. Soft Sponge Material: Unique cylindrical sponge design with 6 vertical stripes to catch floating debris without attracting your fish. 2. Good Filtering: The sponge captures larger waste particles, mechanically cleaning the water without trapping the fish. 3. Multifunction Use: Bio sponge filter can be used as breeding filter or auxiliary filter. As a pre filter unit by installing an external or top filter. 4. Cleaning Fish Tank: Fish tank sponge filter is a great way to clean your fish tank and grow useful bacterium that is good for fish. 5. Instruction: Take an air hose, connect one end to your air pump and the other end to this filter and have a check valve on the air hose to avoid water backflow and air pump damage due to power outages. Specification: Item Type: Aquarium Sponge Filter Material: Sponge Tube Length: Approx. 5cm / 2.0in Inner Diameter of Pipe: Approx. 12mm / 0.5in Outer Wall Diameter: Approx. 15mm / 0.6in Sponge Height: Approx. 7.8cm / 3.1in Bottom Diameter: Approx. 5.5cm / 2.2in . Package List: 3 x Aquarium Sponge Filter3 x Hard Air Tube Note: Please allow 0‑2cm / 0‑0.8in error due to manual measurement.