Shuguang Treasure Cv181-z Vacuum Tube Matched Pair Replace Cv181 Cv181-t 6sn7 The"Shuguang Treasure" as a result of Shuguang's 50-year of expertise in vacuum valve design and production. Improved vacuuming technology during production process to clear signal background. Key assembling process is manually completed by a small number of senior technicians with 30+ years of experience. 60 extra parts selection and matching processes are adopted to ensure premium quality tubes, compared to the Shuguang generic clear glass tubes. Package Included: 2 pcs  Shuguang Treasure series CV181-Z Vacuum Tube(Matched pair)