The pin shows the user whether the coupling is securely locked or not. When the red signal pin is in the ‘in’ position, you can be rest assured that the coupling is securely locked and ready for the journey. The signal and lock pin is always located on the left-hand side of VBG’s couplings.Fits to: VBG 575-3; 590VR-3; 5310D-3; 760-3; 795VR-3; 795V-3; 750V-3; 7310D-3; 4140D-3; 5200D-3