139

2.25" TUBE SHIELD - vintage metal protective cover used for vacuum tubes, primarily designed to reduce radio frequency interference (RFI) and physically secure tubes in their sockets. Stamped with the EIA code "139," which identifies Cinch as the manufacturer, these shields are commonly found in vintage audio equipment from brands like Fender, Marshall, and Ampex - 0.85" OD - 2.25" HIGH - SPRING INTERNALS - MEDIUM VERSION - The "139" designation typically refers to a specific size and attachment style, though dimensions can vary slightly depending on the specific sub-model (e.g., short vs. medium).
Attachment Style: Most use a J-Slot (twist-lock) mechanism with an internal spring to hold the tube firmly.
Tube Compatibility: Frequently designed for 7-pin tubes like the 6AU6 or 9-pin tubes like the 12AX7, depending on the diameter and height