These NMR tubes are manufactured out of ASTM Type 1 Class A glass, commonly referred to as Pyrex® 7740 (Corning), Duran® (Schott Glass), or Kimax® KG-33 (Kimble) glass.

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 under any other application where large temperature variations are required in the experiment.