In a word they work. I have Top Hats on my driver tubes (Brimar EC88) and the difference was astounding. Now, I use the word astounding the case of an AudioPhile, I hear it and I can't go back, the average joe may not hear anything. At about $70.00 for a pair you can't miss. If your tubes are the slightest bit ringy, you should try a set. I think they also absorb some of the Rf coming out of and attempting to enter the tube. Mike
