@tksteingraber
1. The two Cossor tubes you mentioned are customized tubes. Besides retail, Psvane also manufactures tubes for many audio and musical instrument brands worldwide. Due to the differences in performance and application environments required by each brand, these products cannot be directly compared with our retail products. Moreover, we have confidentiality obligations to our OEM customers, so I am sorry that I cannot provide an accurate answer to this question.
These tubes are currently discontinued, but distributors may still have stock for sale.
2. The Mark II you mentioned is part of the ART series and is currently still available for sale.
3. The Treasure z black glass you mentioned is part of the Treasure series, which is still available for sale. However, the Treasure series is a collaboration between us and distributors and is not part of our classification hierarchy.