Valken Airsoft got also their own Tracer unit for use on airsoft guns. In this video get a quick a understanding on their Tango Tracer Unit works... "The Valken Tango Tracer Unit is a barrel mounted tracer unit for airsoft rifles and pistols. It's improved illuminator uses two high powered UV LED's that enhance BB glow activation for an ultra bright trace.

This rifle accessory has a removable, rechargeable lithium polymer battery, and charges quickly with the included micro USB cable (wall plug not included). A full charge will last over 22,000 rounds, or up to 10 hours constant on. It has an intelligent motion sensor that turns the tracer unit on after 3 BB's fired, or turns off after idling for 40 minutes.

The Valken Tango Tracer Unit is just like the Valken Kilo Tracer Unit, but longer. We recommend any Valken ASL Series AEG with the tracer unit."