Gonna assume you mean a PT Cruiser. Chrysler uses a weird proprietary form factor that doesn't conform to single DIN or double DIN, but is somewhere between them in size. GM sometimes uses a 1.5 DIN stereo, but Chrysler's isn't any DIN standard at all.
To put this stereo in, you'll need an install kit from Walmart/Autozone/any car stereo place. This will adapt the weird Chrysler opening to a Single Din opening. You can't use a Double DIN stereo. Single DIN are the shorter stereos while Double DIN are the bigger ones that are nearly square.
Here's the install kit you'll need:
http://www.scosche.com/car-audio/product/19
And I believe this is the correct wiring harness to plug into the stock stereo wiring:
http://www.scosche.com/car-audio/product/220
And a how-to site for doing the install yourself, including wiring it up correctly:
http://www.installdr.com/
Overall, Chrysler vehicles are a real PITA because no stereo equipment they use is standardized stuff.