8mm septa cap for chromatography vials United Arab Black 8-425 Open Top Screw Cap with 8mm Red PTFE/White Silicone Septa 1.5mm Thick. Gc Vials at Thomas Scientific of a screw cap vial with the integrity of a crimp vial, I-D vials have write-on patches graduated at 0.5, 1.0 and 1.5 ml.