I re-tubed my VT100iii w/matched winged "O"'s and 6H30's from the Tube Store and biased them myself. Leonard at ARC walked me through the process before I did it, even though I did not buy the tubes from ARC. No problems and fine results. I don't agree with Cyclonicman's suggestion to keep ARC tubes around in case of a problem, to deceive ARC. There's right and there's wrong and that aint right.