Aug 20, 202 · Precision molding bottlenecks increase the processing power of autosamplers. 20ml 8mm Screw Top Headspace Vials for GC. 8mm Magnetic Metal Cap with Center Hole for more convenient for the automatic injection needle to perform sample injection.Generally speaking, the Septa in the 8mm Closures uses a double-sided compound of Silicone and PTFE