Vials are flat-bottomed glass containers with either screw-on tops or stoppers. They come in many sizes and shapes and hold small amounts of liquids or solids. The ones in lab drawer should all be 3-dram vials with plastic stoppers. Glass is ubiquitous for vials. While dozens of plastic materials are on the market, manufacturers usually produce vials using polyethene or polypropylene. Polyethylene has excellent impact resistance (unlike Glass) and high flexibility. Polypropylene shares these qualities but can also boast resistance to extreme temperatures.