This adapter is designed for radios that do not have DC voltage for bias on their mic connector.
Kenwood - 4 pin connector
Kenwood - 8 pin connector
TS-590 - this also resolves the 'issues' with audio distortion
Yaesu - 8 pin connector
FT-747, 757, 767, 736, 840, 890, 990, FT1000 or FT1000D
PLEASE ADVISE ON YOUR RADIO TYPE SO I SHIP THE CORRECT ADAPTER, EMAIL W2ENY@YAHOO.COM
More on the TS-590, W1AEX has drawn up a fix to the audio distrortion problem. He's got a pretty informative website: http://www.w1aex.com and shows a schematic of his 'fix'.
That's all fine and dandy, try and fit all that in the mic connector.
This is why I went with the battery box option and just moved on.