The R129, introduced in 1989, returned the model to exclusively 2-seater status as were the gen 1 and gen 2 SL-Class vehicles prior to 1964. The R129 was the first Mercedes-Benz model to feature a button-activated, fully automatic, hydraulically-operated folding roof, V8 and (later) V12 engines with four valves per cylinder and projector lens HID headlamps (introduced in 1995). The R129 was the first convertible/roadster to be fitted with automatic rollbar deployment in the event of rollover. The rollbar could also be raised or lowered with a touch of button if desired. The automatic rollbar facilitated safety and security of the occupants without compromising the clean look of the R129. In 1992, R129 was the first SL-Class to have a V12 engine option (600 SL/SL 600) and to have official AMG variants (500 SL 6.0 AMG, SL 60 AMG (V8), SL 70 AMG (V12), SL 73 AMG (V12), and then SL 55 AMG (V8)). The R129 was the last SL-Class to be offered with a manual gearbox.

For the US market, R129 was the first SL-Class to be offered with six-cylinder inline engine from 300 SL-24 (named as 300SL) since the 1971. For 1995, a larger 3.2-litre engine was introduced...