 These early Jeeps are frequently referred to as "flat-fenders" because their front fenders were completely flat and straight, no different than on the original WW II model (the Willys MB and identical Ford GPW).The CJ-4 exists only as a single 1951 prototype, and constitutes the "missing link" between the flat-fendered CJ-2A and CJ-3A/B, and the subsequent Jeeps with new bodies, featuring rounded fenders and hoods, beginning with the 1955 CJ-5, first introduced as the military Willys MD (or M38A1).The restyled body was mostly prompted to clear the taller new overhead-valve Hurricane engine.