Strong Blackburn UK pair.

Test 3750/3750 & 3900/3900 for GM where min is 2600 on a calibrated Hickok 539-B tester.

Listening tested for excessive noise and microphonics in a Maxi-preamp 2 tester.

All tubes are guaranteed good or may be returned for a full refund.

Please see our other items for more vintage tubes & audio.

We combine orders for shipping.

We don't change values for customs.  

Thank You.