These JST cables are handy for making quick connections. They're pretty solid and lock together nicely. The latch keeps the cable from coming apart easily. In this project, we'll use them to as a clasp for the necklace.
The cable set is fairy long, about 16cm long. You have the optional to use the full length of the cable, if you'd like. I'm my build, I cut them short so that I could hook up 30AWG wire, which is thinner and a bit more flexible. I measure both ends to be about 35mm in length. Admittedly, I trimmed them down shorter near the end of the build to adjust the overall length of the necklace.