These Wilmad-LabGlass NMR economy sample tubes are designed for use in all NMR spectrometers and are guaranteed to fit tightly in any spinner turbine and have zero NMR background. Each 5mm tube meets precise wall thickness to ensure they fit tightly in spinner turbine, these tubes have the best OD tolerance in the industry and a 30% thicker wall than other products. All tubes are made from borosilicate glass and manufactured in an ISO 9001:2015 USA facility. Caps are not recommended for use with samples dissolved in chloroform-d or acetone-d6. Guaranteed to fit tightly in any spinner turbine and have zero NMR background NMR tubes are constructed of ASTM E438 Type 1 Class B borosilicate glass Camber and concentricity values listed are the Total Indicator Reading (TIR) 100% visual and physical inspection ensures quality, including physical dimensions and surface defects NMR tube is 7" long by 4.947 ± 0.019 mm OD with a 0.43 mm wall thickness. Tube features 3.8 micron concentricity and 3.8 micron chamber