Headspace Vial. Often Purchased with: Vial Storage Rack for 6, 10, or 20mL Headspace Vials, 36 Vial Capacity, Polypropylene, ea. 18 mm Magnetic Screw-Thread Headspace Caps and PTFE/Red Chlorobutyl Septa, 1,000-pk. 18 mm Magnetic Screw-Thread Headspace Caps and Blue PTFE/Silicone, 1.5mm thick Septa for SPME, 1,000-pk.