Features: Latest version: 12AX7B electronic bile duct with internal isolation plate, can replace ECC83 electronic tube. Higher durability: After rigorous testing for humming, noise, and microphones effects, it is considered one of the best electronic tubes in eletronic tube family. Full voice: soft and delicate, you can hear some detail that you couldn't hear before. Professional testing: It pair the electrode current and mutual conductivity, and passed professional life testing, aging testing, and sound testing. Perfect upgraded: The 12AX7B tube shows you the differences between sound and simple music sound playbacks. Specifications: Material: Glass+Metal Size: approx. 57x22mm/2.24x0.87inch Function: This is a high u low noise small nine pin flat tube used for voltages amplification in amplification circuits, generally used for inverting drive push-pull amplification circuits Scenario: Various sound devices that can be used for the first stage amplification of high gained amplifiers Package Includes: 1 Piece 12AX7B Electronic Tube note: Please allow 1-2cm errors due to manual measurement. Please allow for slight color differences due to different display resolution.