Replacement Sponges: These sponges are designed to replace the original sponges that come with the Sunsun 302 series of canister filters. They serve as crucial components of the filter system. Filtration Efficiency: The sponges play a key role in mechanical filtration, effectively trapping and removing debris, particles, and impurities from the aquarium water. They are part of a multi-stage filtration process within the canister filter. Compatibility: These spare sponges are specifically designed for use with Sunsun's 302 canister filter model. It's essential to ensure that your canister filter is of the correct model (302) before purchasing these replacement sponges.