fully-fledged M cars have larger "M" badges on the grille and/or trunk, wheels, steering wheel, gearshift and door sills with the model number (e.g., "M4" or "M5"). The exceptions include the M Roadster and M Coupe models, both Z3, Z4 and 1 Series variants, which only have an "M" badge with no number displayed on the boot. However, these cars are still proper M cars. BMW has offered these 'M Sport' options on their standard vehicles since the late 1970s which explains why these vehicles carry M badges straight from the factory. In comparison, vehicle maker Audi also employs this same type of nomenclature. There are fully fledged 'S' models (S4, S5, S6, S7 and TTS), as well as an optional 'S'-line package that can be equipped to their standard vehicle lineup. An example of 'M'-badged vehicles in recent times includes the 5 Series and 6 Series only having a choice of either a manual or automatic transmission, but the 'M' Sport package had an optional Sequential Sport Gearbox (SSG) (a gearbox similar to the M5 and M6 (SMG)) until after the 2007 model year. Exclusive M cars Two models, the M1 (1978–1981) and XM (2022–present), are not pinnacle versions of an existing BMW model, but rather, are ground-up performance models produced and sold exclusively in their M variant. Sometimes labelled as "M Original" cars, these models represent flagship performance and design for the M brand. M Performance models In 2012 BMW introduced a new category for M cars, branded as M Performance, designed “to bridge the gap between M Sport variants and the outright M high-performance models.“ The lineup included the diesel-powered M550d in saloon and touring body styles, X5 M50d, and X6 M50d, marking the first diesel-powered BMW models to ever carry M-badging. The gasoline-powered M135i debuted shortly after. BMW has since announced M Performance variants of nearly every model in their lineup, including three new electric models, the i4, ix and the i7. Exceptions The 2010 X5 and X6-based M vehicles bore their normal model designations followed by the "M" stripe badge (the X5 M and X6 M). If the nomenclature followed tradition, then they would have had an MX5 and MX6, already used by Mazda. The Z3-based M Roadster and M Coupe bore numberless "M" badges as standard fitment. The first generation Z4-based Z4 M Roadster and Z4 M Coupe bore their normal model designations followed