Hope your having a good day, our 2 pack filters are made of high quality biochemical sponge, safe and non-toxic, harmless to water and fish. Can be used with confidence.Size: height 8cm/3.15inch, diameter 4cm/1.57inch, inner hole diameter 2cm/0.79inch. Suitable for external filter inlets and various inlets for aquarium products and fish tank.ITS Multifunctional: to prevent dirt from entering the filter container, thus prolonging the service life of the filter media. Protects small fish and shrimp from sucking into the filter insert, is good for their healthy growth. Easy to Use: It can be quickly and directly connected to the filter, use directly in the water inlet easy to take out to clean.