Amber glass screw thread vials offer protection from harmful light and uv rays for light sensitive products. These general purpose glass vials are made of type i borosilicate glass, providing exceptional resistance to heat shock and chemical leaching. Ready to clean vials are designed for users who prefer to use their own cleaning process. ready to clean vials are fully assembled with 24-400 polypropylene caps and a friction fit .015 in PTFE (similar to PTFE) disc. both cap and liner can be washed, heated or autoclaved depending upon your application. The PTFE disc is chemically inert, and will not interfere with your test results.