For containment of NMR samples that are sensitive to light. Constructed from Pyrex glass, the tubes are subjected to a high temperature ion exchange reaction to impart the light blocking properties to the glass surfaces.
In order to form stronger bonding, a special optical coating technique is used (as opposed to the usual amberization of other tubes found on the market). A maximum blocking per cent results for wavelengths
Results may vary and depend on the nature of the sample.