Fuel injectors are a key component of your vehicle's engine, allowing the precise mixture and timing of fuel delivery for optimal performance. The numbers on a fuel injector indicate its size and spray pattern, both of which have an effect on how well the engine runs. A larger number indicates a bigger sized injector and wider spray pattern, meaning more fuel will be delivered to each cylinder in less time - ideal for high-performance engines. On the other hand, smaller numbers can help reduce emissions by providing finer atomization (smaller droplets) with less fuel wasted in combustion and lower exhaust temperatures. It is important to know the exact specifications you need when looking to replace or upgrade your existing set up as different types may require different tuning parameters such as pulse widths or valve timings. Knowing these details can help ensure that you get the most out of your new system while avoiding any potential problems down the line!