Aijiren Tech™ 20 mm Headspace Vials, Septum, and Caps. 20mL; 20mm; Clear. Headspace vials are available in clear or amber glass with a round or flat base, a crimp seal with a beveled or square edge finish, or with a screw-thread finish. Headspace vials, septum, and caps can be purchased in various quantities separately or together as