Injector nozzles interact with Pistons in Combustion Chambers. When the Piston is drawn away from the Spark plug, the Injector Nozzle sprays a fuel and air mixture into the Combustion Chamber. By pumping the fuel/ air mixture that is necessary for the engine to continue running, Injector Nozzles must be kept in excellent condition for an engine to run at maximum efficiency. Some important information for selecting the correct Injector Nozzle(s) is the type of part needed; fuel type, fuel mixture formation (common rail, distributor-type injection pump), length, shape & size and date limitation of the unit. As car manufacturers regularly update certain peripherals and design of their models, some Nozzles will only be suitable for particular models of certain years.