One side of the adapter is recessed to allow the filling probe to seat fully.
Please check your fill port orientation, this is made for a more or less horizontal fit as pictured, any other may need the mount removing to fill the gun.
Easy fitment:
-Simply loosen the single bolt for the barrel band
and remove it.
-Place the barrel band inside in the grove on the
rail adapters front side -some light pressure may be needed.
-Slide the new adapter and barrel band back onto
the barrel/air tank evenly.
-Retighten the bolt for the barrel band