There are two different physical clocking standards for NMEA-2000 Micro-C connectors. Electrically they’re the same, but the internal pin set is rotated inside the plug, which rotates the whole T-piece body by about 45°.
That’s why your new backbone T doesn’t sit flat with the others — it’s a different connector coding, not a faulty part
Why does this exist?
Originally, several marine electronics manufacturers sourced M12 connectors from industrial CANbus suppliers who used different coding / clocking standards:
Industry sourceCodingIndustrial CAN / DeviceNetB-codedMarine-specific NMEA 2000A-coded (what most people expect)
Over time the marine world mostly standardised on A-coded, but:
Raymarine (older gear)
Maretron (some early stock)
Garmin (some OEM backbone parts)
Cheap Amazon / AliExpress N2K kits
…still appear in the wild with B-coded rotated shells.
We occasionally find this, but there is not much we can do about it, as if we sold the other type, we would still have issues with orientation compatibility.
I would look to purchase another Tee the same as you have, or stand the existing backbone Tee strip off the wall a little with a packer so the 45 degrees has space to connect.
If space allows, you could flip the whole backbone so the 45 degrees is coming away from the wall instead of going towards it.
We can ask customer to send a pic of the mounted backbone they are trying to attach it to so Baz can take a look and advise?