to be fitted with the iconic 15-hole, flat-faced alloy wheels characteristic of Mercedes-Benz cars of the 1980s and 1990s. The alloy wheels were nicknamed 'gullideckel' or manhole covers, because they resemble manhole or drainage covers in Germany, which are consistently round in shape with a series of 15- or 16-holes around the outer edge, often within a concentric ring. Gullideckel wheels in a variety of diameter and offset specifications were later incorporated into the facelift versions of the W126 S-Class, R107 SL and W201 190E series, and were also the 'non-option' wheel on the R129 SL-Class roadster. Much of the 124's engineering and many of its features were advanced automotive technology at its introduction, incorporating innovations that have been adopted throughout the industry. It had one of the lowest coefficient of drag (Cd) of any vehicle of the time (0.28 for the 200/200D model for the European market with 185/65 R15 tires) due to its aerodynamic body, that included plastic molding for the undercarriage to streamline airflow beneath the car, reducing fuel consumption and wind noise. It had a single windscreen wiper that had an eccentric mechanism at its base that extended the wiper's reach to the top corners of the windscreen (more than if it had traveled in a simple arc). The saloon/sedan, coupés and convertibles had optional rear headrests that would fold down remotely to improve rearward visibility when required. This feature was not available for the T-model because of its specific layout (no space to store the retractable headrests), but the estate serially came with a "neighbour-friendly" rear door that was pulled in the shut-position silently and automatically by a sensor-controlled servomotor. This allowed the use of a tighter fitting rear gate, minimizing the cabin noise in the T-model - sometimes an area of concern for station wagons. The estate cars (chassis designation S124) came in 5 or 7-seat models, the 7-seater having a rear-facing bench seat that folded flush luggage compartment cover and an optional (in the US until 1994) retractable cargo net. To provide a flat loading floor with the seat folded down, the T-model's rear seat squab was mounted about higher than in saloons, robbing rear seat passengers of some head room. The S124 estate continued in production alongside the new W210 until the S210 estate launched more than a year later. A two-door coupé version was also built, with the chassis designation C124.