According to the instructions it takes 1000ml. I've never used it, so I accept that number as being accurate. I got this in a lot with other items I needed.
The Patterson tank does not include the regular reels, although I do have some that could be available. I need to inventory them.
This setup takes exactly 1L and will process 6 sheets of 4x5" film. Gentle agitation is the key, or else the sheets will come dislodged and in contact with one another. Some users have reported difficulty with the thin IR films from Rollei (IIRC?).
It's a very convenient way to develop 4x5"; just have to get the agitation right and possibly adjust your times accordingly.