The 6BH6 vacuum tube is a high impedance, medium gain signal amplifier pentode.  It is popular in the pre-amp stage of audio amps.  These have been matched by close Gm values and sold as a pair.

• Tested on a Hickok 6000A tester
• All pairs test Gm > 2000 Gmhos
• Matched within +/- 25 Gmhos of each other
• Condition:  New old stock

Feedback from one of our customers:

Far too many Ebay tube sellers think matched tubes have the same printing on the tubes. This pair of 6BH6 pentodes indeed have the same Transconductance or so says my recently calibrated B&K 707 tube tester ! At last , a decent pair of input tubes for my customers Marantz 8 amplifier. Better than 5 stars IMO . CHEERS !! - fixit82