I just wanted to put a quick note on here about the necklace cords I use.
I get imitation leather necklace cords. I buy these cords already made. And the seller I get them from doesn't mention what the metal components are made of. These are around 18" long and have a 2" extender chain. So they can be a total length of around 20". There will be some size variance to these (sometimes the cord is closer to 17" than 18").
While I try to make sure all the connections look sturdy, I would treat these as more of a "display chain." I include the cords so the pendant can be worn right away until the buyer can obtain a better chain/cord. I put the pendants on larger size bail rings to make it easy for you to change out the cord.