What is the correct holding flat nut for this Harting M12 cable assembly

I have a Harting a-coded PFT cable assembly [Harting 21033176505] that i will install onto my control panel. I cant seem to find the proper part number for the correct size for the holding flat nut. Can anyone help me out or forward to the correct resources? Thanks in advance.

Hello NJC, welcome to the DigiKey TechForum.
The datasheet says it has M16x1.5 threads, so a correct Jam Nut would be 277-8039-ND. Please check the datasheet.