Yes, I know. I saw your post in the tubes section. The new Ruby tubes look like the preferred series version. I posted a response in that forum for reference.
http://forum.grailtone.com/viewtopic.php?f=16&t=73036
Preferred series are very similar to the TAD 6L6GC-STR, shiny black oxide coated plates, dual halo getters. Tubes sound great in the JP2C but I found it much brighter than the Mesa STR440 (Ruby 6L6GC-MSTR). I would say they come close to the SED (=C=) at a much lower cost per tube. Not as dark as the TAD 6L6GC-STR (loved those in my Mark V before I broke off the guide pin and inserted it in the socket indexed improperly). If the tubes have a black plastic base, you may want to mark on the base where the guide pin key is located. Preferred series has a different material on the base but I marked the location where the key is in the event the plastic material is as poor as the TAD. Funny though, after I went back to the Mesa tubes, I was thinking of going back to the brighter tube.