Official Replacement Pre-Filter for the Survivor Filter PRO and Electric PRO X Unlike our Competitors, Survivor Filter Backs up all its filtration claims with reputable North American Testing Water is pre-treated with the 0.1 Micron Filter, before it reaches the other internal filters. Can be easily cleaned after every trip up to 100,000 Liters (26,417 Gallons) for re-usable enjoyment Backwash After Your Trip: Backwashing helps flush out any small particles that may be clogging and slowing down the flow rate of your filter. The Pre Filter can also be backwashed when out on the trail. Simply use the water that has already been filtered by the Survivor Filter PRO. Outer Shell Made of Military Grade BPA Free ABS material To replace, simply remove used Pre-Filter and replace with new Beware of imitations and use only Official Survivor Filter replacement parts. All Survivor Filter products are shipped from North America.