Our headspace vial caps come in either 11 mm, 18 mm, 20 mm or 22 mm sizes. Most used headspace vial caps are crimp cap style. Headspace screw caps are used with magnetic directed headspace instruments for better alignment. Aijiren headspace vials and caps are the perfect fit for a wide variety of applications, including pharmaceutical, environmental, energy and fuels, forensics, materials science, biopharmaceutical, proteomics, and metabolomics.