Due to the larger size of the sponge, we squeeze it to make shipping easier. After placing the sponge in water for a period of time, it will return to its original size. If you mind, please place your order with caution. Thank you very much for your understanding. Features: The biochemical sponge filter provides biological filtration for the aquarium and helps stabilize water quality. Increase oxygen solubility. It works silently and is very durable and will last for many years. Good penetration and easy to clean. The perfect filter accessory for your fish tanks and aquariums. The foam is cuttable and suitable for various fish tanks. Specifications: Product name: Aquarium sponge filter Color: Black (as shown in the picture) Sponge size: 50cmx50cmx2cm/50x12x2cm/40x30x2cm/40x30x3cm Reminder: 1. Soak the sponge in the aquarium water for 5 minutes before use, which is beneficial to nitrifying bacteria Easier to colonize. 2. Always use room temperature aquarium water to rinse the sponge, never hot water. 3. Must be connected to an air pump for use. Includes: 1x Aquarium Biochemical Sponge Filter