When Katadyn first released their Pocket Filter, they rated the service life of their ceramic filters at 50,000 liters. If you calculated the flow rate of one liter per minute, you would have to pump your Pocket Filter for over a month nonstop before considering a replacement. If you're one of the few who has been out in the field long enough to pump 50,000 liters through your Katadyn Pocket Filter, here's your replacement ceramic element, you lucky dog.