Best tube dampers that you have used

Of the 29 tubes in my current setup, not one has a damper on it.  Not for lack of trying them, everything from Herbies to Mapleshade.

If you look long and hard enough you can always find somebody who doesn’t hear it. - Old audiophile expression 😀

I use the Pearl Tube Coolers with a bit of a modification.  I solder a wire to them which I run to chassis ground.  Not only do they drop tube crown temp 10 to 15 degrees they eliminate any RF interference via the grounding and provide damping.

I understand that wrapping thin strips of meat around your tubes may seem messy, but this will both damp the tubes and cook the meat. Win win. 

I've had very good success with Mapleshade Halo tube dampers. https://shop.mapleshadestore.com/Tube-Gear-Upgrades/products/316/. The Halo tube dampers come with grounding straps. As one of my audiophile friends said, "...what a steal at such a great price..." I put the Halos on my tubes after hearing the SQ difference in his system. I just got two more Halos because my new preamp has 4 tubes instead of the 2 like in my previous preamp.