Gibson had made forays into radical body shapes (the Flying V and Explorer) in the 1950s, but they failed to meet expectations. The president of Gibson, Ted McCarty, hired car designer Ray Dietrich to design a guitar that would have popular appeal. Under Dietrich, the Firebird took on the lines of mid-50s car tailfins. Dietrich took the Explorer design and rounded the edges. The most unusual aspect is that the guitar is "backward" in that the right-hand (treble) horn of the body is longer than the other. Thus, the original Firebirds were unofficially referred to as "reverse". The Firebird is the first Gibson solid-body to use neck-through construction, wherein the neck extended to the tail end of the body. The neck itself is made up of five plies of mahogany interspersed with four narrow strips of walnut for added strength. Other features were reverse headstock (with the tuners on the treble side), "banjo" tuning keys, and mini-humbucking pickups. The Firebird line went on sale in mid-1963 with four models distinguished by pickup and tailpiece configurations. Unlike the Les Paul and SG line, which used the terms "Junior", "Special", "Standard" and "Custom", the Firebird used the Roman numerals "I", "III" , "V" and "VII".