I have their 6st 150 GPD Reverse Osmosis RO+DI Water Filters#ROH-6B-150 (under the aquarium without tank category).
The tank's aren't as cool as you'd think. They are like 3-5 gallons, which imo is no where near enough water to have on hand. Even making 150 gpd, it's a pita to have to wait any time when you're ready to use water. I got a 60 gal brut for $25 and it's perfect, but you can get brut's down to like 25 gallons, and many other 15+ gallon containers. All are imo way better to use than the tanks they come with.
If you don't mind the mineral content you can get smaller stage unit and skip the DI, it's primarily removing minerals. Also these things don't come with inline TDS meters like more expensive filters. If you want inline tds or pressure gages you will have to buy them separately. A dual inline TDS meter was $30-40, and a pressure gage was $8 with a few dollars to T it inline.
I can also say they were easy to work with. I had a fitting that cracked in shipping and leaked slowly. I emailed them, and an hour later I got an email back that he had sent me a replacement part, and also an adjoining part just in case it had been damaged as well. New part got here fast, one of my better customer service experiences.