NORELL Select Series NMR Tubes are specifically designed for high-resolution NMR. These tubes are manufactured out of ASTM Type 1 Class A glass, commonly referred to as Pyrex 7740 (Corning), Duran (Schott Glass), or Kimax (Kimble) KG-33 glass. Several key properties that make this glass type desirable for NMR are its high degree of thermal shock resistance and low expansion coefficient. This allows for a greater margin of safety from breakage when used in variable temperature applications and freeze/thaw cycling, or any other application where large temperature variations are required in the experiment.