The first models of the 911 had a rear-mounted 130 PS (96 kW; 130 hp) Type 901/01 flat-6 engine, in the "boxer" configuration like the 356, the engine is air-cooled and displaces 1,991 cc (2. 0 L) as compared to the 356's four-cylinder, 1,582 cc (1. 6 L) unit. The car had four seats although the rear seats were small, thus it is usually called a 2+2 rather than a four-seater (the 356 was also a 2+2). A four or five-speed "Type 901" manual transmission was available. The styling was largely penned by Ferdinand "Butzi" Porsche, son of Ferdinand "Ferry" Porsche. Butzi Porsche initially came up with a notchback design with proper space for seating two rear passengers but Ferry Porsche insisted that the 356's successor was to use its fastback styling. 7 prototypes were built based on Butzi Porsche's original design and were internally called the Porsche 754 T7. Erwin Komenda, the leader of the Porsche car body construction department who initially objected, was also involved later in the design.