The Colortune plug kit is a simple and effective way to tune petrol and LPG 2 and 4 stroke engines. It is easy to use and works on the principle that the combustion flame burns a particular colour depending on the fuel mix. The Colortune is a spark plug with a glass insulator viewing window so the flame is visible. The colour of the flame inside the cylinder shows the state of the air:fuel ratio - yellow indicates a rich mixture, blueish-white a weak mixture and a Bunsen blue flame a balanced mixture. By adjusting the mixture screw to get the correct flame colour the engine can be tuned for optimal fuel economy and performance. The kit also includes a viewscope with adjustable mirror so that the flame can be seen where engine access is restricted. Fits most petrol engines with additional adaptors available for vehicles with other sizes of spark plug.