It took me a lot of searching to find just the right black necklace cords to sell with my pendants. I really like this one.
18 inches (45.75cm) in length it looks like twisted silk cording, but it's really made from durable black rubber, which will not fray like silk, and has quality 925 sterling silver end caps and clasp instead of the usual silver plate. At 2mm in diameter it is sturdy enough for heavy gemstone pendants, but has an elegant look. End caps are streamlined so any pendant with a bail larger than 3mm will slide easily onto this necklace cord.
My dress form has a large 16 inch (40.5cm) neck. Necklace cord will fit differently on someone with a smaller neck. Pendant is not included.