Official Replacement Carbon Filter for the Survivor Filter PRO and Electric PRO X Filter Systems. Made from Food Grade Coconut Shells. Can be re-used up to 2,000 Liters (528 Gallons) before replacing. Designed to Help improve the taste and odor of water and to help catch the chemicals that make it through Stage 1 (Ultra Filter Pre-Filter). Outer Shell Made of Military Grade BPA Free ABS Material. To replace, simply remove used Carbon Filter and replace with the new one Beware of imitations and use only Official Survivor Filter replacement filters to keep your Survivor Filter PRO in top condition. Durable and Well-Made: The Carbon Filter attaches using a “push and twist” motion to keep it secured onto the internal Ultra Filter. Features an “O” ring where it connects to the other replacement filter, which helps keep the device watertight.