(!!) (Recommended Pair) 6CS7 GE Canada NOS black plates 1965-1969 (18/11.2ma and 20/9.6ma) (close Gm)1 pair) 6CS7 GE Canada NOS black plates 1965 1969 1 tube) 18ma Gm=4500 and 11. 2ma Gm=2200 1 tube) 20ma Gm=4800 and 9. 6ma Gm=2100 Tested on Amplitrex Good Ma triode #1 = 10 11ma, Good Gm = 2000 2200 Good Ma triode #2 = 20 25ma Good Gm = 4000 4500 for: Leben CS 600 integrated amp Leben CS 660P power amp