The most important purpose of the air filter is to guarantee the enough protection of the engine against the probable abrasion in all of the dusty surroundings. The dust holding capacity of the air filter must be suitable. The most considerable part of the air filter is the filter element that consists of high grade cellulose fibres. The other important part in panel and circular type filters is polyurethane. By a very little strength to air flow, air filter holds micro-particles and dust. Because of being small and light they can be attached under all type of the engine bonnet. The service is easy and cheap. Heavy duty air filters are used in too dusty surroundings especially in the work vehicles. By means of heavy duty air filters the vehicles that have powerful engines can not be effected from dust environments, so there will be no problem in the working conditions of the vehicle because of high combustion efficiency of the air in the system. Sport air filter SCT-Vertriebs GmbH developed special air filter for sport/racing cars. This special design permits very high flow rates, minimum restriction and maximum filtration, and very long filter life as well.