To allow for a uniform classification and easy comparison of car rental prices, the Association of Car Rental Industry Systems and Standards (ACRISS) has developed the ACRISS Car Classification Code coding system. This describes the size, door count, gearbox type (manual/automatic), and whether the car is air-conditioned, encoded into four letters. The first letter in the Acriss Code represents the general classification of the vehicle (e.g. Mini, Economy, Compact etc.). The second letter specifies the vehicle variant on offer (e.g. 4 Door, Estate, Convertible, SUV etc.). The third letter is generally used to specify the transmission type, although it can also be used to describe how many wheels drive the vehicle, and the fourth letter describes the fuel type and whether the vehicle has air conditioning or not.