iTracer is a full-function electronic kit for Airsoft guns which contains 3 units: iTracer Unit iTracer CD (Commander Display) iTracer SCU (Shooting Control Unit) You could use these 3 units in different combinations depending on the type of your Airsoft guns: ● Use all 3 units together: Suitable for AEG ● Only Use iTracer Unit and iTracer CD: When you don’t need to use the multiple (parameter: 1~20) round burst function or if your Airsoft gun is gas-powered, spring-powered or hybrid. ※Because iTracer SCU itself is an electronic accessory, which should be connected between AEG and AEG battery, it could only support AEG which doesn’t contain original built-in MOSFET or 3-round burst function. ● Only use iTracer unit: When you don’t need to use any counting function (like count-up or count-down), you can only attach iTracer Unit on your Airsoft gun as the brightest tracer unit.