They are AFAIK, direct replacements in the 6922/6DJ8/7308 family. But you will get loads of opinions on which are the best in which product in which position. Try Joe's Tube Lore at audio asylum for detailed descriptions of just about every variant of each tube family. However, be aware that Russian and (I think) Chinese companies have bought the rights to many of the premium NOS tube names and there are widely varying opinions about their quality and sound. There are also TONS of fakes and pulls being sold as NOS, esp on Fleabay.
