This is a used Heil model SM-1 Microphone Mount.  It is a professional suspended shock mounting system designed to isolate handheld dynamic microphones from low-frequency mechanical vibrations, stand noise, floor thuds, and surface thumps.

 

The SM-1 is designed for use with the slim-line Heil Sound microphones, such as the PR 20. It will also work with other brands of microphones such as Electro-Voice or Shure.  It does not work with the Heil PR-35 or PR-37.

 

It has standard 5/8″-27 threads.

 

There are a few places where you might see some minor signs of use so please view all the photographs before bidding.