This is a brand new in the OEM package a Antenna Works (Metra) 

Antenna Adapter # 40-GM28

General Motors Antenna Adapter Cable

For 1993 GM Factory radio with mini "barbless" connector 

to 

1988-1992 GM antenna with mini "Barbed" plug.

This adapter is required to install a 1993-UP factory radio into a 1988-1992 GM vehicle equipped with a "barbed" antenna plug.