Made of Pyrex® borosilicate glass (unless otherwise noted) for compatibility with ground joints, valves, and vacuum racks. Precision ground and highly polished for spinning stability and highest resolution.Tubes have round bottoms and include a sandblasted marking spot for labeling samples. Tubes are thin-walled unless otherwise stated. Tubes that are 9 in. L are for making standards and for use with tip-off manifolds. Precision Wilmad NMR tubes are suitable for high field NMR spectroscopy. Caps included.