Welcome to the Dell Community @SFerg
Have you removed the "Bottom Cover" to see what your options are???
Dell Latitude 12 Rugged Extreme — 7204Series Owner's Manual:
I have 5 or 6 of this model.
I can pull the cover from one in the morning but it may not be the same configuration as yours.
Thanks for that very informative information.
You could also include that the mSATA is enclosed in a "Removable" proprietary caddy.
There are no caddies that can include an M.2 SSD.
Since it would be a limited market it would not be profitable.
There are 2 internal connecters but I have not explored any other options.
Until I can do some testing it would be unprofessional of me to suggest anything else.
These caddies are so hard to find: " At a good price"
If any one has a source that is under $50 US please PM me.
I can trade E6420XFR original caddies.
Many thanks for all of the information. I think ive worked out that a samsung 860 evo will fit as it B/M keyed and similar to what is installed now, a crucial mx500.
I wasnt aware that the was a space internally so that could be another option.
Be careful with the terminology. B/M keyed refer to M.2.
This system uses mSATA - which is a different form factor. It's mini-PCIe SATA:
NOT the now much more common M.2 SATA:
If you acquired the system used, it looks like someone used an M.2 SATA to mSATA adapter card.
Any M.2 SATA drive that physically fits can be used in this -- but not nVME.