National Scientific Screw-Thread Sample Storage Vials National Scientific White Storage Caps With Ptfe Liner. Combining top-notch and uncompromising quality with an affordable price the Thermo Scientific Screw-Thread Sample Storage Vials Thermo Scientific White Storage Caps With Ptfe Liner B7815-20/ 66030-779 can fulfill your laboratory needs while still offering a great value for the money. Manufactured under the most stringent conditions these vials eliminate leaching of ions and provide a consistent pH for the duration of the sample storage. Available in clear and amber borosilicate glass. Clear glass is Type I Class A 33 expansion borosilicate glass. Choose amber glass for light-sensitive samples. National Scientific Screw-Thread Sample Storage Vials National Scientific B7815-20 White Storage Caps With Ptfe Liner