20ml Crimp Headspace Vials Features. 1. 20mm crimp headspace vial is widely used in Headspace and GC, GCMS application. 2. 20mm Aluminum Crimp Cap Seals and Vials ensure that a proper seal is made for this demanding application. 3. Vials are manufactured of borosilicate glass and include a write-in patch for sample identification. 4.