In August 1967, the A series went into production with dual brake circuits and widened (5. 5J-15) wheels still fitted with Pirelli Cinturato 165HR15 CA67 tyres. , and the previously standard gasoline-burning heater became optional. The Targa (meaning "plate" in Italian ) version was introduced. The Targa had a stainless steel-clad roll bar, as automakers believed that proposed rollover safety requirements by the US National Highway Traffic Safety Administration (NHTSA) would make it difficult for fully open convertibles to meet regulations for sale in the US, an important market for the 911. The name "Targa" came from the Targa Florio sports car road race in Sicily, Italy in which Porsche had several victories until 1973. The last win in the subsequently discontinued event was scored with a 911 Carrera RS against prototypes entered by Ferrari and Alfa Romeo. The road going Targa was equipped with a removable roof panel and a removable plastic rear window (although a fixed glass version was offered from 1968).