This pattern can be used with a variety of yarn at different gauges as explained in the note below.

From Knitty.com

If you would like to use up a bit of yarn from your stash, knit up a gauge swatch in stockinette st using the needle size of your choice, and bind off.

The important part of the gauge for this pattern is along the cast-off edge, since this is the portion that determines the length of your necklace. Measure your swatch just under the cast off edge and determine the # stitches per inch.

To adapt the pattern for the gauge of your yarn, plug your number into the following equation:

(# stitches per inch) x 30 + 6 = number of sts to cast on

If necessary, add or subtract 1 or 2 to this number, so that you have a multiple of 4 sts + 2.