Let's be honest! I don't know of ANY music amp that uses 4 6V6's in a quartet/quad. (There may be some Hi-Fi amp that does) I could have ordered 2 pairs (duets), as I now want to try these in a Traynor Darkhorse and a Fender Super Champ X2 as well as the delightful success in my Fender 65 Deluxe Reverb. The description of these valves recommends them in the Deluxe Reverb, which I totally endorse, but there are only 2 in a Deluxe! - I just LOVE the sound though! Alright - I've now searched and there is the Bogner Goldfinger 45 and the combo version on this site, but I've never encountered them before. Very efficient and professional of Thomann (as usual) to provide these as a matched quartet as spares.