Features: 1. High quality: our aquarium filter cotton is made of high-quality sponge with good filter effect. Biochemical cotton filters clean dirt, stabilise water quality. 2. Protect shrimp and fish: the filter cotton is filtered in multiple layers, which completely avoids sucking shrimp and fish. 3. It reduces the noise of the air pumps and consumes little power. Increase oxygen solubility without generating operating noise. It is suitable as an external filter or above purification unit. 4. Increase the oxygen content of the aquarium: harmful substances are broken down by nitrification on the sponges and converted into substances that are harmless to fish and go back into the tank. It is suitable for storing and observing different fish. 5. Widely used: this aquarium filter is small and easy to hide behind the plant. It fits in any corner and is ideals for shrimp tanks, breeding tanks, beta aquariums, water tanks, turtle tanks, aquariums, goldfish, young fish or other fish. Notice: 1.Actual color may be slightly different from the image due to different monitor and light effect 2.Please allow 1-3cm deviation due to manual measurement Description: Material: sponges Size: As picture show Choice 1: 1x Sponge Filter Choice 2: 2x Foam Sponge Roll