Mark,
I put those made of copper, because I think it is best for connections, but it's just a personal choice...
Because if you look at the lugs of the electrical circuit in the lighthouse, they are all in copper...
And I put the insulator over the wire before you crimp the terminal.
If you want to replace the insulators must be cut the terminal put a new insulator and crimp a new terminal.
You want to talk about the models that I surrounded?
That I bought at AES, the second link.
Gerard