Honestly, it's the clasp.
No matter how many times I've done it, I'm always a little worried that they are vulnerable to breaking where the clasp connects. I reinforce them, I knot them multiple times, but after so many years of wire work, they still seem like they are hanging on by a thread (yup - they are...)
I've been toying with the idea of making beaded rope cuff bracelets for a while and finally got my first ones finished.