This is the fine coiled spring of wire called French wire, bullion, gimp or purl (!). It is used to reinforce and protect the silk where the strung pearls are attached to the clasp. This is 3.5mm diameter.(1.6mm internal) The length is 45 cm which will be enough for about 30 necklaces (phew!) . It gives the most professional finish to any pearl necklace. This type resembles french knitting rather more than a simple coiled spring and would work for really chunky items.
We recommend that you cut up the whole length as soon as you receive it, as this stuff will kink, bend, stretch, squash and generally distort if you so much as look at it the wrong way.
Use fine nail or embroidery scissors or snips