All cars competing in each class must adhere to a strict set of regulations. As in some well known racing events, like NASCAR and NHRA, sanctioned events often require a minimum vehicle weight. In such cases the interior is stripped, and the required weight is achieved by adding ballast that allows precise control over weight distribution.
Along with weight requirements, safety requirements are present . Requirements differ for different classes. Roll cages, fire extinguishers, reinforced bucket seats, seat harnesses, and the like are some of the required safety modifications. Roll cages may be difficult to install when the original equipment interior is present. Some tuners will have “gutted” interiors. Some tuners omit features that many ordinary drivers would find desirable or necessary, such as audio systems, air conditioning and soundproofing.