We have been selling thread adapters for a while but the latest batch are a step up in quality. They are machined from solid brass and have a standard 3/8″ female thread that will fit most modern mic stands. They can also be supplied with 5/8″ on request.
It fits this RCA77B perfectly.
These fit the following microphones….
Most RCA 44, PB140, PB144, 74b, 77B, 77DX, MI-4010-A, BK-11.
Some (but not all) models of the RCA Varacoustic.
Sony C38, C48, FV300, Some C37s.
Many Aiwa, Toshiba and Matsushita ribbon mics
Syncron / Fairchild AU7a
Some older Amperite mics