Using your Fluval AC Series Filter Insert Bags is a breeze. First, pick the right size for your filter from the available options: 20, 30, 50, 70 or 110. Then, open the bag with the convenient closure and fill it with your chosen loose filter material like carbon, peat or bio - rings. After that, place the filled bag into the media compartment of your filter. It's important to note that the product is going through a packaging change, so you may receive either the new or old version. When it comes to maintenance, you can easily remove the bag from the filter. You can reuse these bags, just clean them regularly to keep your aquarium water clean. These bags are suitable for both freshwater and saltwater aquariums, so no matter what kind of aquarium you have, they'll do the job.