There are two types of Headsapce Vials produced by Aijiren, one is 18mm screw neck headspace vials and the other is 20mm crimp neck headspace vials. Among the two headspace vials, 20mm crimp neck headspace vials are favored by more customers because of their good sealing properties and suitable for gas chromatography analysis. Many gas chromatography experiments are inseparable from 20mm headspace vials.