Oct 28, 2021 · Cap/Septum has a natural Pre-slit Blue polytetrafluoroethylene (PTFE) and white silicone septa are convenient and minimize contamination from handling.Cap/Septum tested by head space GC to ensure proper curing of silicone polymer.2ml HPLC Vials caps and septa with most close space tolerance and caps and septa meet standards set by governing bodies.