Abstract: An improvement in a unit closure for a vial container, which helps ensure the smooth depression of the unit closure with a relatively small force from the air-expelling posture to the hermetically sealing posture and eliminate a fear of destroying the unit closure and container in depressing the protector whereby hermetic sealing and tamperproof are achieved. To this end, the locking means is of flexible locking tongues arranged such that they are inclined diametrally inwardly of the skirt and upwardly towards the ceiling of the protector, whereby, upon depressing the unit closure to its hermetically sealing posture, the locking tongues deflect radially outward of the skirt and, on completion of the depression of the unit closure, the locking tongues snap resiliently into place underneath a flange of the mouth of the container to hold firmly the unit closure in the hermetically sealing posture.