Cuvette. ND20 Headspace 20ml Crimp Vials. 20mm Aluminum Crimp Cap Seals and Vials ensure that a proper seal is made for this demanding application. Vials are manufactured of Clear, Type 1 Class A or Amber, Type 1 Class B borosilicate glass and include a write-in patch for sample identification. Both flat and rounded bottom vials are available.