This is a Streamline 5 stage Pure-Tel RO with a 75 gpd membrane & 3/8" tubing for higher flow rates. It also comes with a faucet & 2 gallon pressure tank if they'd want to use it. Here's the picture from their website:
The DI is a SpectraPure Max Cap D2 Dual Stage Add-On Kit for the 5 stage RO. Here's the info on that:
Everything you need to add a dual stage DI to your existing RO system. SpectraPure, Inc.® Revolutionary MaxCap DI ™ cartridge has over 3 times more capacity than any other Mixed-Bed or Hi-Silica removal deionizing cartridge. Install 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.
SpectraPure’s Dual MaxCap DI™ System comes with:
2-Position Housing & Mounting Bracket
MaxCap DI â„¢ Cartridge
SilicaBuster â„¢ DI Cartridge
Dual-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 Wrench
Retail-Ready Package
DUAL-STAGE ADD-ON
(ADD TO YOUR RO SYSTEM)
In many applications, the MAXCAP DIâ„¢ (DI-MC-10) is installed up-stream of a Mixed-Bed or Hi-Silica removal cartridge. For example, if the RO water entering the MAXCAP DIâ„¢ has 20 ppm TDS (Total Dissolved Solids), the original DI cartridge may process about 400 gallons of pure DI water. By placing a MAXCAP DIâ„¢ cartridge in front of the original cartridge, 1200 gallons of water will pass through both cartridges before the MAXCAP DIâ„¢ is exhausted. The original DI cartridge will be only one-third exhausted. A second MAXCAP DIâ„¢ will process another 1200 gallons and the original cartridge will now be two-thirds exhausted. Only after a third MAXCAP DIâ„¢ cartridge processes another 1200 gallons will the original cartridge finally become fully exhausted.
That's 3600 gallons purified with only 4 (3 MAXCAP DIâ„¢ + 1 Mixed-Bed) cartridges, not 9 (9 x 400 = 3600).
I've attached the brochure for it if you'd like to check it out. They advertise that the Shedd Aquarium uses their systems. This is their FAQ section Untitled Document & you can figure out flow rates & percent of rejection. Everything is dependent on what kind of water they are putting into the RODI too. If they aren't conditioning the water before it goes in the GPD will be a lot lower because they're leaving calcium, iron, magnesium, sediment, radium, ect. in their water. They also have to consider water temperature and what the their incoming water pressure is. There really isn't a definitive answer on what this unit will do unless we can determine the other factors but best case scenario is approx. 75 gallons per day. | 
