23 x 85 mm 6 dram (22 ml) Clear borosilicate vial with 20-400 black phenolic polycone lined cap attached. clear screw thread vials offer maximum visibility. These general purpose glass vials are made of type i borosilicate glass, providing exceptional resistance to heat shock and chemical leaching. Attached black phenolic (thermoset) caps with polycone liners form an exceptionally tight seal and offer a good chemical barrier. This liner molds itself around the sealing areas of the finish as the cap is screwed on, virtually eliminating leakage, evaporation, contamination, binding and backing off. great for everything from liquids, to soaps, to macro-invertebrates.