A filling neck to feed fuel into a motor vehicle tank using a filling nozzle, exhibiting the following features: a slotted drive ring comprising an insertion portion conically tapering toward the vehicle fuel tank, the cross-sectional constriction being less than the filling nozzle's cross-section; the drive ring, facing the fuel tank comprises, on at least one side of said gap, a locking segment; the drive ring is configured in floating manner in a cup-shaped housing portion of the filling neck, the outside diameter of said ring being less than the inside diameter of the cup-shaped housing portion; a sealing element is associated with the distal end of the drive ring, blocking access to the tank in its closed position; the drive ring's locking segment engages and keeps the sealing element in the locked position, and moves into the open position when said drive ring is expanded by the filling nozzle.