While, at first glance, the Volkswagen Beetle's exterior changed little for 1956, a number of updates were made to the vehicle, both inside and out. Tubeless tires were now standard equipment, for instance, and the optional sunroof (which VW noted could be opened, closed, or adjusted while driving at full speed!) was smaller and made of plastic, replacing the previous year's cloth sunroof. Minor alterations were made to the gear shift knob (now curved) and the heater knob (which was moved forward), and the horsepower for the starter motor was increased. In addition, the gas tank was redesigned to provide more luggage space, and the front seats were now wider and adjustable. Features of the car, which were noted in VW's brochure for the '56 Beetle, included vent wings in the front windows, which could be pivoted to provide fresh air to the cabin, and a built-in heater. The car's air-cooled, four-cylinder engine produced 36 horsepower.