Aug 1, 2022 · 2021 - 10 - 25. flat bottom headspace gas chromatography with PTFE septa DWK Thermo Scientific™ 11mm Clear Snap Cap, PTFE/Silicone. Polyethylene (Cap), Silicone/PTFE (Septa) Septum Blue PTFE/White Silicone, Pre-slit Vial Closure Size 11mm Thickness (Metric) 1.0mm Quantity 100 Type Snap Cap with Septum Item Description 11mm Snap-It Cap, 6mm.