This Bundle includes THREE items: the SpectraPure SilicaBuster Semiconductor Grade (Non-Indicating) High Capacity Shell 10" SuperDI Cartridge (Model DI-SB-10HC); SpectraPure MaxCap (Non-Indicating) SuperDI High-Capacity 10" Cartridge (Model DI-MC-10HC); & MarineAndReef Towel. These are the two DI cartridges that comes stock with the SpectraPure units, and they should be replaced at the same time. The MaxCap comes first and the SilicaBuster second, and when used together in this order they have maximum effectiveness. SpectraPure's MaxCap DI Replacement Cartridges are the heart of the MaxCap Series of products. When placed ahead of your existing DI cartridge, the life of your downstream DI cartridges will increase by four times or more and lower your DI production costs by over half. And now, the SuperDI MaxCap DI Cartridges have even greater capacity than the standard-shell cartridges. SpectraPure's SilicaBuster Mixed-Bed Multi-Layer Deionization Cartridges are fabricated with semiconductor grade resins for highest possible purity water. They are capable of producing 18 meg ohm-cm resistivity water. The MarineAndReef Aquarium Cleaning Towel is a durable, lint-free microfiber towel. 19" X 15".