Image Credit: Goss Scientific
An NMR tube is a thin glass walled tube used to contain samples in nuclear magnetic resonance spectroscopy. Typically NMR tubes come in 5 mm diameters but 10 mm and 3 mm samples are known. It is important that the tubes are uniformly thick and well-balanced to ensure that NMR tube spins at a regular rate (i.e. that they do not wobble), usually about 20 Hz in the NMR spectrometer.
When selecting NMR tubes, cost is important to consider. Prices range from 1 to 20 dollars per tube. A cheap tube will often have widely varying wall thickness or a pronounced bend, making spinning more difficult. More expensive tubes do not guarantee results, but merely reduce the chances of error or failure due to the tube itself.