Navien, PeakFlowE, Replacement Media Cartridge for 19.875" (inch), GXXX001327
 
For the 19.875" (inch) version.
Anti-scale system designed to treat hard water.
PeakFlowE works by converting mineral ions in the water to a microscopic crystal form that does not attach to the internal surfaces of the water heater.
Chemical and salt-free
Quality tested under pressure at the factory
1 year warranty from date of purchase.