Medium (12.6*4.7*3.1 inch) Applicable fish tank size:35-55cm Multi Layer Aquarium Fish Tank Filter with Waterfall Oxygenation Suitable for 20-25 Gallon Fish Tanks, Flexible Mounting, Dust & Splash Protection Feature: 1. Multi Layer Filtration System: Designed for a range of tank sizes, including 20-25 gallon fish tanks, this advanced aquarium filter features a multi chamber system. It efficiently cycles and filters water, removing impurities and maintaining crystal clear water stability. 2. Waterfall Oxygenation: Suitable for any aquarium filter setup, the waterwheel design enhances oxygenation in fish tanks. It generates abundant bubbles, significantly boosting oxygen levels, which is essential for a healthy aquatic environment in tanks of all sizes. 3. Ultra Quiet Operation: This fish tank filter operates with minimal noise, making it perfect for peaceful environments. 4. Flexible Mounting Options: Suitable for various fish tank filters, including those for 10 gallon and 20 gallon setups, this filter offers internal and external mounting options. This flexibility allows it to adapt to different aquarium configurations and placement needs. 5. Dust and Splash Protection: This filter for fish tanks includes a dust cover, preventing debris from entering and water from splashing out. It's a practical addition for maintaining a clean and tidy aquarium, whether you use it as a 10 gallon -25 gallon aquarium filter or for larger tanks. Package includes: 1pc medium filter box (without filter material, assembly required)