The Empty Cartridges Can Be Refilled By Using A Filter Media Such As Anion Resin, Cation Resin, Activated Carbon, Ferrolite, Active Sand, Silica Sand, Manganese Zeolite Etc.. That Needs To Fill The Cartridges Into The Media Is Not To Be Stuffed Full Of 100% With The Contents Of The Filter Media, But Simply By Charging 75% Only. This Is Due To Provide A Space / Cavity For Water To Be Able To Proceed Dangan Media Perfectly So There Is Clogged Or The Water Can Not Get Out Of The Filter Housing.