When I had a Cyber 211 amp, I tried GE, RCA, United, and Billington Golds, a new 211 tube. IMHO there was no question that the RCAs were clearly the best, United next, and then GEs. The new 211s, as usual, cannot compare. I guess it is a lost art to make vacuum tubes. As I understand it GEs and RCAs were made in the same factory although they are of quite different construction.