Is there a functional difference between these two connectors?



If you used the NM one on FMC condiut, what would happen?

  1. It will work fine, no problem doing it
  2. It will work fine, but inspectors would get mad
  3. It won't work/is bad/dangerous for some reason
  4. other? haha

2 Answers 2


The correct answer is number 3.

The FMC clamp has a barrier that prevents the flexible conduit from entering the box.


A cable clamp has one job

It's supposed to clamp the cable in a way that the cable won't fall out of the hole, and will not damage the cable.

Notice the clamps are different shapes (assuming these are even pictures of the actual product, who's to say?)

So it goes without saying that the different shape will result in different clamping and damage characteristics.

However, it looks like the clamps may differ only in the cover plate, so if you have already installed the wrong thing, you may be able to correct it by swapping cover plates instead of rewiring.

  • the one I had is actually a combination coupler (homedepot.com/p/…) - unless I'm crazy that looks identical to the FMC link in the original post, even though this one is marked NM? Aug 2, 2019 at 23:59
  • @DavidDoria the combination coupler in your comment here is a coupling designed to connect NM cable to EMT conduit. It is not a (box) connector, so serves a different purpose in a different place.
    – Armand
    Oct 6, 2022 at 3:15

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