Industrial & Scientific" /> Composed of extra thick amber 203 borosilicate glass for both sturdiness and magnification of contents while diminishing light sensitivity Micro-vial has a screw thread top to accept the PTFE-faced 14-B white rubber-lined solid top closure Cylindrical shape provides solid balance; flat bottom facilitates free-standing capability Conical cavity allows maximum retrieval of contents with a syringe needle Durable white ceramic enamel graduated scale and large marking spot on each bottle