The current BMW model lineup is split into what is referred to as "Series", traditionally identified by a single digit - e.g. the 3 Series. In 2004 BMW announced plans to make odd-numbered series saloon/sedan and estate/wagon models (BMW calls its estates/wagons Touring models), while even-numbered series will be two-door coupés and cabriolets. This convention started informally in 1976 with the introduction of the 6 Series and later continued in 1989 with the 8 Series, but died off when the latter was discontinued in 1999. This practice was revived as the Z4 replaced the aging Z3 roadster in 2003 and continues as the new 6 Series augments the existing BMW 5 Series. BMW M GmbH (previously: BMW Motorsport GmbH) is a subsidiary of German car manufacturer BMW AG established in May 1972 with just eight employees. BMW M, also known as M-Technik or just "M" (for Motorsport) was initially created to facilitate BMW’s racing program, which was very successful in the 1960s and 1970s. The first racing project was BMW’s 3.0 CSL; in the late 1970s the first modified street legal road cars were produced for the contracted racecar drivers as their personal vehicles. By 1988, the number of employees had risen to 400.