The decision of BMW to produce motorcycles with in-line engines saw the bikes in these model series receive a totally separate designation.The development designation ‘K’ was adopted as a series badge. As with the boxer models, the ‘K’ was followed by a number derived from the displacement of the in-line engine. BMW followed the same pattern with the single-cylinder machine that went on sale in 1993. This model series was given the designation ‘F’, referring to the ‘Funduro’ concept. More recently, the new generation of lightweight single-cylinder machines presented in 2006 took on the letter ‘G’.