Closely matched quad (4 tubes) of vintage military-grade NOS JAN GE 5654W vacuum tubes (the "W" in the tube designation refers to a ruggedized, military grade tube). These vintage 5654W tubes are an upgrade for 6J1, 6AK5 and EF95 tubes used in headphone and other audio amplifiers. These carefully selected tubes can help bring out the best musical fidelity in amplifiers and pre-amps that utilize 6J1, 6AK5, 5654 and EF95 tubes. The four tubes in each set are meticulously matched for both mutual conductance and plate current using an Amplitrex AT1000 tube tester. All tubes in our Platinum Grade Matched Quads test at NOS level, with Gm of 5200 micro-mho or higher and plate current above 7.3 mA (tested in fixed-bias mode at a plate and screen voltage of 120 V and a grid voltage of 2 V).  For each set of four tubes, mutual conductance and plate current are both matched within 3%!  Each tube box is labeled with mutual conductance and plate current.  Other quality checks performed include shorts/leakage, gas, noise and a life test (the life test involves remeasuring mutual conductance after reducing filament voltage by 10%). In addition, as a final check, all our matched pair and matched quads are audio-tested in an amplifier prior shipping.  These tryuly are the best-of-the best.