Art Audio only sells Grade A Tubes from Sophia Electric in matched pairs or quads.
Sophia Electric applied all expertise learned from the past to this new flagship Royal Princess 300B model. It has the best virtues of both Princess mesh plate and Princess carbon plate 300B tubes and sound light-years ahead of any 300B tubes made in the history including both Sophia Electric Princess Carbon Plate 300B and Princess Mesh plate 300B tubes that won worldwide praises.
From the outside, the Royal Princess 300B tube looks similar to Carbon Plate Princess 300B (share the same glassware enclosure), however, the design philosophy is quite different and the internal design and material is different as well. You have to listen to it to hear the dramatic sonic upgrade. I am confident that you will report the positive outcome once you have tried the Royal Princess 300B tubes
This tube usually ships within 2-4 business days.