Abstract: A flexible elastomer closure plug mat presents a plurality of protruding hollow septa closure plugs depending from the mat's lower face. The mat and protruding closure plugs are preferably formed of silicone rubber, with a thick layer of polytetrafluoroethylene or TEFLON® durably bonded to the lower face of the mat and to the outer faces of all of the arrayed plurality of closure plugs. The arrayed plurality of closure plugs are dimensioned for telescoping insertion into the open tops of a corresponding plurality of sample vials held in a well plate, and for frictional engagement therein.