A sealing device relates to a plug that includes a crusher mechanism, where the sealing device includes one or more glass layers positionable in a wellbore. The glass in a barrier phase bears against at least one seat or support sleeve arranged axially displaceably in the wellbore, where the at least one seat or support sleeve bears against the glass by means of a supporting hydraulic fluid in a pressure support chamber, the seat or support sleeve being configured to be released, be displaced axially, and to crush the glass when the supporting hydraulic fluid is released from the pressure support chamber.