I have 5 extra new prefilter sponges that I did not used.Sponge, that can be attached to the intakes of any filter intake strainer. It's acts as a mechanical prefilter that do not let any small particles such as small fragments of dead plants to clog media inside your filter. Sponge prolongs maintenance period of any filter: canister or HOB. It can be clean once every week or two.You'll be surprised how clean your media baskets are and will stay clean for long time. I use these sponges on Wisper 10 HOB filter, Eheim pro3, AquaClear 20, AquaClear 110. Also this sponge is necessity for tanks that is raising fry. It does not let any baby fry to be sucked into the filter. It is also acts as biological media in the fry tank. Dimensions: 4 inches tall, diameter-2.5 inches. Price: 4.50 each. Shipping $2.00 via First Class Mail. If you want to buy all 5 sponges -$22.00 shipped.