GC Headspace Vial - Aijiren Product Details ; Part No. SACA001, SACA002-II ; Description, Red PTFE/White Silicone Septa, 13mm Black Screw Polypropylene Cap, 8.5mm Centre Hole, Red PTFE/White 18mm Screw Thread Metal Cap for GC Vials It fits perfectly with the matching 18mm magnetic metal screw cap and PTFE/silicone septum.