certified headspace gas chromatography with cap Sigma-Headspace Vials Autosampler Vials, Caps, and Closures - Fisher Sci 202 - 07 - 06 Chromatography Thermo Scientific™ 20 mm Headspace Vials, Septum, and Caps 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