Headspace vial caps are available in a variety of materials including aluminum, bimetal, and steel; headspace vial cap septa are available in PTFE/silicone, 100PCS Caps Crimp Top 20mm Aluminum Hole PTFE/Silicone 1000pcs 9mm Screw Thread Autosampler Vial,PP Close Top Cap+PTFE Silicone Septa.