The glass sample vials require aluminum caps for sealing, The vial’s neck is precisely molded to improve the autosampler processing. Crimp Top Headspace Vials gas chromatography mass spectrometry. Crimp Headspace Vial. Short Neck. 100pcs/pk. C0000196. 20mm Open Top Aluminum Crimp Cap (10mm hole) with 20mm Natural PTFE/White Silicone Septa 3mm Thick.