MT-RJ connectors do not have a 2.5 mm ferrule, found on SC and ST connectors. This means you cannot use any of the standard tips that come with the FiberInspector to measure MT-RJ connectors. You will need this optional tip:
Testing MT-RJ patch panels:
Model name: NF360 Part number: 1614309 Description: MT-RJ VIDEO PROBE ADAPTER TIP*
*If you put an MT-RJ coupler on the MT-RJ patch cord, you can use this adapter to test MT-RJ patch cords as well.