Sep 09, 2020 · Sep. 9th, 2020. Aijiren’s 20ml Headspace Vials are divided into two categories, 18mm Screw Thread 20ml Headspace Vials and 20mm Crimp Top 20ml Headspace Vials. Aijiren’s 20ml Headspace Vial is made of borosilicate hydrochloric acid glass, which is extremely inert and not easy to react with chemical reagents.