Plug and play into the factory radio wire harness.  
Allows installation of an aftermarket radio using the existing factory wiring and connectors.
No cutting of factory wiring is needed.
Works with select vehicles only.
Metra 70-9221 or equivalent depending on stock availability.
Might not be compatible with factory amplified systems.

Works with the following vehicles:

Volvo:
2001-2009 S60
1999-2006 S80
2001-2007 V70/XC/Cross Country