Bodykit or body kit is a collection of exterior modifications to a car, typically comprised of front and rear bumpers (fenders), side skirts, spoilers and sometimes front and rear side guards. There are many companies that offer alternatives to the original factory appearance of the vehicle. Body kits components are designed to compliment each other and work together as a complete design. Despite this, the 'mix and match' approach is often seen on cars, where the front of one body kit will be matched with the rear of another for example.

Automotive body kits are usually constructed of either fiberglass, polyurethane or in some cases carbon fiber - a popular and lightweight material. Polyurethane is popular with car enthusiasts because it is more resistant to damage and does not crack in cold weather. However, carbon fiber kits are not as highly regarded among automotive enthusiasts, because it is very costly for a minimal weight difference.
Factory fitted body kits are now becoming more common, perhaps in response to the growth of the aftermarket tuning industry in the late nineties and onwards. Many manufacturers now work in-house with their motor sport divisions to develop styling upgrades.

Ground effects
Ground effects are parts of an automobile's lower body designed to enclose the gap between the bottom of the fuselage and the ground. The purpose of ground effects are to deflect air around the car rather than under it, reducing the lifting effect of air passing under the car at high speed. Lift reduces the tires' contact with the road, resulting in reduced control. This effect differs from genuine Ground effect, in which airflow is manipulated in such a way as to create downforce on the car, pressing the tires harder onto the road.
Ground effects can be part of the vehicle's original design, or aftermarket parts added later (body kit). It should be noted that aftermarket body parts generally simulate the appearance of a vehicle in ground effect and usually do not provide significant aerodynamic benefit.