This pin goes inside 1/8 Inch Quick Disconnect Male to turn it into a 1 way valve. Many refillable tanks has a 1-way valve at the quick disconnect to allow air to enter but not exit.
Dimension: End to end 13.26mm, Rod Diameter: 2.78mm Head Diameter: 5.87mm
Dimension: End to end 13.26mm, Rod Diameter: 2.78mm Head Diameter: 5.87mm