The Hawach caps are all manufactured from high-quality polypropylene and are suitable for 9 mm HPLC vias and fit screw thread sample vials with excellent quality and performance. Application of 2ml 9mm HPLC Vials: Our 2ml 9mm HPLC Vials and screw caps are ideal for HPLC and GC instrument platforms in a variety of applications including pharmaceutical, environmental, energy, fuel, forensics, materials science, biopharmaceuticals, proteomics, and metabolomics.