Using a replaceable activated carbon filter and a pleated glass fiber filter the Katadyn Vario can purify 2 liters of water per minute. And, for truly filthy water, the Vario employs an additional ceramic pre filter to prevent the grime from gumming up the more sensitive fiber and carbon filters. Best part about the ceramic filter is that it can be cleaned off easily with a scrubbing sponge. Clean water is a must have for any survivalist or prepper. They’re also great for camping trips.