Check the listing for details. 12-Pack Pre-Filter Sponge for Aquarium Fish Tank Filter Replacement Foam Cover. Condition: New. Listed at 8.99 USD. Key Feature: Lifesaver: Keeps baby fish, shrimp, and snails from getting sucked into hob filters, power heads or canister filters by simply putting a pc of this pre-filter sponge over the intake. Improve Filtration: Does a good job in catching flake fish foods, plants and any other large particles floating in the water keeping the tank cleaner and last longer between cleanings. Maintenance: Rinse the sponge roll periodically based on the bio load of your aquarium tank. The material holds up well to being rinsed and reused and allows great water flow. This pre-filter sponge also can be used to dampen the outflow and make the water more stable for your betta. This prefilter sponge provide both mechanical and bio filtration For a snug fit, check the size you need carefully before placing an order. Note: The hole doesn't go all the way through the sponge. Package includes: For 0.4”: 12 pcs of prefilter sponge, 1.4"D X 2.4"H; the inside hole diameter is 1cm/0.4” For 0.6”: 12 pcs of prefilter sponge, 1.6"D X 2.8"H; the inside hole diameter is 1.5cm/0.6” For 0.8”: 12 pcs of prefilter sponge, 1.8"D X 3.2"H; the inside hole diameter is 2cm/0.8” For 1”: 12 pcs of prefilter sponge, 2.2"D X 3.9"H; the inside hole diameter is 2.5cm/1”