The SpectraPure MaxCap D-2 Retro Kit 2 Station includes everything you need to add a dual stage DI to your existing RO system. Includes:SpectraPure Model MC-DI-2-102-Position Housing and Mounting BracketMaxCap DI CartridgeSilicaBuster DI CartridgeDual-Probe TDS Meter (Determines when the MaxCap DI TM Cartridge is exhausted. When the output TDS exceeds 75% of the input TDS, change the Cartridge.)Universal Filter WrenchUser Manual (pdf file in new window)The MaxCap DI cartridge has over 3 times more capacity than any other Mixed-Bed or Hi-Silica removal deionizing cartridge. It's installed after your existing RO system to remove any unwanted algae growth in your aquarium. This incredible break-through in DI cartridge technology will enable you to produce DI water at less than half of any other dual stage DI systems.