Refer to the Headspace vial compatibility chart to help you quickly identify those consumables (vials and seals) suited to your own instruments. Headspace crimp or screw ND18 and ND20 Vials Aluminium crimp caps and liners 20 mm diameter (ND20) (available with butyl, butyl/PTFE, Pharma-fix, silicone/PTFE, silicone/aluminium, UHT silicone/PTFE seals)