The 6 step E-6 Tetenal kit is a 5L kit. Same as Kodak. I always use it to the maximum capacity that Kodak indicated on their own kit (500ml to dev 4 rolls of 120). Never had a problem, even as the kit ages.

I got it here:
WebbCam LLC
241 North 12th Street
Philadelphia, PA 19107-1722
(215) 923-8380