Up for auction are two RCA 5751 black plate, triple mica vacuum tubes in very nice condition. Both tubes were tested on a Hickok 547 tube tester where 1500 micromhos is mutual conductance and 900 is a minimum. One of the tubes tested at 1700 and the other at 1710 micromhos. You might could say that they are a matched pair, but for sure they both tested very well. THANKS FOR LOOKING!!!