I have that Tube Lore II book on order. Looking forward to getting it. I didn't know Bob had a HF-300 rig. Don, you are probably now the only ham in the world running that tube. I have never seen any for sale at hamfests. They must have been around more in the '60s and '70s. It's definitely one of those tubes that can't be shipped, like 450THs, and maybe 250THs. Anything with a long plate structure. I've looked for them on-line and finally turned up some far out website from a vendor to the East, Ohio maybe, that had all kinds of gov't surplus etc. stuff for sale and HF-300s came up in some sort of search you could do on their inventory. I think they were NOS. The price was reasonable but I recall Don that you declined to take them because you have a number already, and they'd probably get smashed up in shipping.