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The DIN size head unit has visible dimensions of 2 1/8" (50mm) tall and 7 1/8" (180mm) wide. There is no standard for the depth of the unit. Most aftermarket head units are a direct fit for this size and an adapter kit will not be required.
Both mid- and full-size cars have the capacity to hold five people, with two in the front seat and three in the backseat. The size of the people traveling in the car affects the choice.