Rapid Fire system - TrueFire FLEX for DualShock™ 4 controller for PS4™ FAT/Slim/Pro consoles.
TrueFire FLEX is a flexible circuit board that requires only 3 solder connections to operate (attachment point + L3 and R3 wires to the ribbon cable).
Undetectable during online play, the system can be installed with or without an additional button to control rapid fire and other functions (then use the Left button on the D-pad to activate/deactivate most of the functions).