When replacing your factory radio with an after-market car stereo, the CWH-634 wire harness is a must for a quick and clean installation. It eliminates cutting your OE radio plug. After connecting it, your install is simple as the wires will color-match and easily connect to the after-market stereo. Without the CWH-634, you would have to cut the OE radio plug and manually test each wire to connect to your after-market receiver.
In addition, because you do not have to cut your OE radio plug off, the CWH-634 allows you to reinstall your factory receiver if necessary. A great example is if you sold your car, but wanted to keep your after-market radio and re-install your factory stereo receiver.