4x 6K4P-EV / EF93 / 6BA6 / W727 (NEW, NOS, OTK). Works in any position. Produced in a glass finger design. Indirectly heated oxide cathode. 7-pin base with button bottom. Foreign analogues of the 6K4P-EV lamp: EF93, W727, 6BA6, 6BA6W, 6BD6, 6F31, PM04, M8101, 5749, 6660.