Tube rattle is caused by the internal components of the tube vibrating against the glass, and most of the time that's from the output tubes that often hang near the speakers. Most new tubes rattle, only a few don't.
Eurotubes damping rings work very well to stop the rattle with any tube. I believe that our member Rick has discovered this as well.
For undamped tubes, double and triple-Mica spacers were designed to stop rattling, and I think that the JJ double-Mica output tubes are available from Eurotubes as well. Mica spacers were designed to do this in the old days, but on most new tubes they're garbage. In the old days, they had more effective "fingers" to brace the tube against the glass, and most modern tubes don't bother making them that way.
But the internal components in modern tubes are generally inferior to NOS, and this can be observed comparing them. I once posted some photos of modern vs NOS in my own stash, the the difference was immediately apparent.
I found the Telefunken-branded JJ 6L6s s don't rattle. They sound nearly as good as NOS, but they're pricier because they go through hand selection and a cryo process that seems to work.
I use NOS tubes in most of my amps, and they don't rattle, but I had serious rattle in my 100 Watt Mesa Lone Star 212 combo with the Mesa tubes, and the Eurotubes damping rings cured it. Nonetheless I replaced the stock tubes with Telefunkens, and they don't rattle, even without damping rings. I think they sound better, too.
