No significant changes were made to the double focusing mass spectrometer part of the instrument, and therefore no change in isotopic ratio measurement performance was anticipated for the NanoSIMS-HR, and none was found (Table ; Fig. ). All measurements were within the precision specified for both instruments, and in this case, all but one had sub-permil precision (1). For the Si isotope measurements, high current analyses with Faraday cups achieved ~10x higher precision for the small (microns) and medium (millimeters) movement test, and ~2x higher precision for the large (10s of millimeters) movement test, relative to the lower current analyses with EMs. The O isotope measurements with Faraday cups and the electron flood gun (e-gun) also achieved sub-permil precision.