Best Answer: A Single Din is the standard size of a head unit (the stereo in the dash of your car) a double din is twice as large. Double dins are good for cars that have large stock head units like a caddyhas. Single dins are good for most cars, that way you can just slide the old head unit out wire the new one and slide the new one in without having to cut your dash any. Good luck. The DIN standard is a radio chassis that's 7 wide and 2 tall. A true double-DIN is simply two DIN units stacked; or a single unit that's the same size as two DIN units stacked. Double-DIN head units became common as CD players became more popular; many vehicle manufacturers (especially of Asian cars) created a DIN CD player for use with a DIN cassette/radio unit.