Update as requested
First photo is the underground connector kit. Must say that it makes a very satisfying connection. The allen screws do the trick. I am told the connection is good for up to 12ga wire. I put three of my lights into the one end, no issue.
Second pic is box of the fixture. They are made in Cave Creek, AZ just up the road from me. Last two pics are of the fixture on its side an with one in place in my fountain. I like the minimal design. At night all you see is a source, the fixture is so small and nearly same color as the gravel.
In talking with the electrical guy, his comment on the wire nut with dielectric grease particularly when installed in gravel like I am, the gravel moves and breaks the bond of the grease in the wire nut.
I now have this wired temporarily to be sure all works. Will let it cycle through 2 or 3 days and assuming all is good, bury it all.
Thanks Baz for the help. Has been good to work through the issues.