in U.S. and possibly other markets, became standard on all trim levels by the late 1980s. The sway bars decreased body roll, but at the expense of some ride comfort and when driven aggressively, increased inside wheel spin. The front and rear bars' diameters were unchanged throughout the model's run. The 900 has a deeply curved windshield, providing the best driver visibility. The dashboard was curved to enable easy reach of all controls, and featured gauges lit up from the front. Saab engineers placed all controls and gauges in the dashboard according to their frequency of use and/or importance so that the driver need only divert their gaze from the road for the shortest possible time and by the smallest angle. This is why, for example, the oft-used radio is placed so high in the dashboard. In keeping with the paradigm of its predecessor, the 99 model, the 900 employed a door design unique in automotive manufacturing, with an undercutting sweep to meet the undercarriage, forming a tight, solid unit when the door was closed. This feature also eliminated the stoop in the cabin at the footing of the door, as seen in automobiles of other manufacturers, thereby preventing water and debris from collecting and possibly entering the cabin or initiating corrosion, as well as enabling passengers to enter and exit the cabin without need to step over several inches of ledge. The 900 underwent minor cosmetic design changes for 1987, including restyled front end and bumpers that went from a vertical to a more sloped design. To save money, Saab kept the basic undercarriage more or less unchanged throughout the 900's production run. The Saab 900 could be ordered with different options. One highly sought-after option was called the Aero or, as it was known in the U.S. "Special Performance Group" (SPG). The Aero/SPG incorporated (depending on the market and model year) a body skirt; a sport-suspension (1987+) that included shorter, stiffer springs, stiffer shocks, and sway bars; leather seats; premium stereo; and air conditioning. Each of these features could also be ordered independently from Saab's Accessories Catalog for fitment to standard models. Another desirable UK option at this time was the fitment of very distinctive Minilite alloy wheels. Initially these had the words 'Minilite' and 'Saab' cast in raised lettering; later Saabs had a similar wheel made by Ronal. Power output varied by model year and market, but