Sound ports. This is a new one to me.
But this M20 now has one. http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=300254596879&indexURL=1#ebayphotohosting
More types here.
http://www.mcknightguitars.com/soundports.html
But this M20 now has one. http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=300254596879&indexURL=1#ebayphotohosting
More types here.
http://www.mcknightguitars.com/soundports.html