I'm also not sure what Bottlehead is shipping, but the TR6-6020 (TRN6-6020) is the right size. Folks recommended the TR6-6015 to me (those are much easier to find) but I am unsure how much the shorter height changes the chimney effect of the heat transfer. (Physics says taller chimneys have higher heat transfer rates, but I have no measurements on how much that 0.5" height change affects these particular tubes in this application.)
If you want to use them just as shields, the 6015 works just fine. I've done that myself. It looks cool, but I have no idea what it's doing regarding heat transfer.
If Bottlehead isn't selling the shields, check out Leeds Radio. They may be one of the few places that still stocks the 6020 size. You can find the 6015 all over the place for a few bucks. Good luck!
Mary
« Last Edit: April 13, 2017, 04:05:03 PM by maryc27182 »
DIY 2-ways (TAD TD-2002, AE TD15M), Stereomour 45
Fostex TH-500RP, S.E.X. 2.1
Eros Phono