A custom car is a phrase that became prominent in American pop culture in the 1950s, an has enjoyed special interest popularity since that time. It relates to a passenger vehicle that has been modified in either of the following two ways. First, a custom car may be altered to improve its performance, often by altering or replacing the engine and transmission. Second, a custom car may be a personal "styling" statement by the re-styler/re-builder, making the car look "unique" and unlike any car that might have been factory finished.