The Plymouth Reliant and Dodge Aries are mid size cars introduced for model year 1981 as the first "K-cars" manufactured and marketed by the Chrysler Corporation. The Reliant and Aries were the smallest cars to have the traditional 6 passenger 2 bench seat with column shifter seating arrangement favored by customers in the United States, similar to larger rear-wheel drive cars such as the Dodge Dart and other front-wheel drive cars such as the Chevrolet Celebrity. The Reliant was powered by a then-new 2.2 L I4 SOHC engine, with a Mitsubishi "Silent Shaft" 2.6 L as an option. The Reliant was available as a 2-door coupe, 4-door sedan, or as a 4-door station wagon, in three different trim lines: base, Custom and SE. Station wagons came only in Custom or SE trim.

Mid-size—also known as intermediate—is a vehicle size class which originated in the United States and is used for cars larger than compact cars and smaller than full-size cars. "Large family car" is a UK term and a part of the D-segment in the European car classification. Mid-size cars are manufactured in a variety of body styles, including sedans, coupes, station wagons, hatchbacks, and convertibles. Compact executive cars can also fall under the mid-size category.