Anyone familiar with 6C33C-B Power Tubes?

Can anyone give me some background on the 6C33C-B power tube? Can you get it in NOS tubes, or is it too new? What brands do you recommend? What amps, besides BAT is it used in? Thanks in advance for any info that you can give me.
Antique Sound Labs uses them in their Ki22Fox integrated and KMP60Fox monoblocks. Check out for some info on buying them. The 6C33 is part of a family of high-transconductance tubes that are tough to design with but can deliver very good rewards if done right. That is about all I know about them. Arthur
Tenor Audio also uses these tubes. They are relatively inexpensive ($18-$25), but I haven't discovered any other manufacturing sources.