Wheaton headspace vials, 20ml or 0.68oz clear, 20mm finish, type i borosilicate glass. Headspace vials feature rounded shoulders and bottoms, allowing for even heating and safer operation at higher pressures. The newly designed top provides a tighter seal with your septa. Vials are manufactured from type i borosilicate glass. (hspace conv pk, 20ml vial, ptfe/ silicone seal) headspace convenience pack, 20ml vials, ptfe /silicone, seal. W225280-02 autosampler vials, glass, 20ml with 20mm pressure-release headspace seals, aluminum seal with ptfe and silicone septa each convenience pack includes 100 chromatography vials and 100 aluminum seals. Warning: this product can expose you to chemicals including tetrafluoroethylene, which are known to the state of california to cause cancer. Prop 65 warning