I received these tubes today, so this is not a long-term review. Replaced two JJs (and I also put a 5751 in V1) in my Rivera Chubster. It made a difference in tone. The amp sounds much smoother, with less mid-range gain or barking. I prefer a Fender Blackface tone in the clean channel, and this tube change was a significant improvement. Interesting though because I have been told that tube rolling doesn't do much for a significant change in tone, and I have been told to use the tube types that came with the amp because the amp was designed around those tubes. Not true here. In this respect, the Rivera seems very accommodating, even though Rivera themselves told me to stick with stock type tubes. Their amp adjusted well. However, I doubt this is true for all amps. For example, I have other amps where I tried tube rolling, and nothing was accomplished - did absolutely nothing to change tone. I guess some amps just have their characteristic tone, and there is nothing I can do about it. Thanks Tube Store for the tube reviews, that helps!!!