3 WAY Holley EFI CAN splitter. The two of the Black male connectors are designated for Dashes, Screens, and other Holley accessories. The single White male connector is designated for the USB-CAN tuning cable(not included). At the flip of the switch, you can disable communication to the accessory connectors, and communicate directly with the main computer. Perfect for firmware updates and other functions that can not be done with multiple devices connected.