I recently sent an e-mail to Amperite, the makers of the 3TF7 and asked if that tube, the 4H4C and the 1HT4 were still available and how much they wanted for new ones. Both the 3TF7 and 4H4C (used in some models of National HRO receivers) were still available, and although the 1HT4 was not, its replacement, the 1HTF4 was. They want $107.00 EACH for them. Gee... Ken Gordon W7EKB