Economical borosilicate gc headspace vials with flat bottom GC Vials ND20 headspace 20ml (Crimp Vials) ,ND20 GC GC Vials ND20 headspace 20ml (Crimp Vials) 20mm Aluminum Crimp Cap Seals and Vials ensure that a proper seal is made for this demanding appliion Vials are manufactured of Clear,Type 1 Class A or Aer,Type 1 Class B borosilie glass and include a write-in patch for sample identifiion.