The car was available as a two- or four-door Torpedo bodied “Tourenwagen”, a four- and (from 1935) two-door “Limousine” (sedan/saloon), a three- or four-seater Cabriolets or as a sporting two-seater.

[4] During the model's final year, Mercedes-Benz announced, in June 1936, the option of a more powerful 2,229 cc 55 PS (40 kW; 54 hp) engine, which was seen as a necessary response to criticism of the car's leisurely performance in long bodied form.

[1] In terms of features and performance the W21 represented considerable progress when compared to its predecessor, and was priced at the same level although it was equipped a little more simply and in standard-wheelbase form was a little smaller.

The appearance of a long-wheelbase version a year after the introduction of the standard bodied car was in part intended to address comments that the W21 as originally launched was a little small to be considered a full-size taxi.

The cars were conceptually similar and even shared an identical 3,050 mm (120 in) wheelbase, although the Opel was lighter, a little less powerful and in terms of performance claims slightly faster.