Border Mill North Coast 4 ply yarns are a mixture of natural and dyed fibers, blended by hand and spun in very small batches in Border Mill's tiny mill in the Scottish Borders. These yards are beautifully soft with oodles of character and impeccable provenance.
Working on a such a small scale, Border Mill can't make perfectly consistent, reproducible yarns. So as well as the occasional slub or the odd knot, you may find some some small inconsistency in thickness or color, even within a batch.
A lot of people like this variation in the yarn, but if you want to avoid any noticeable changes within a section of knitting, as with all hand-dyed yarns, it's recommended to work alternate rows using two different skeins - either throughout the garment or at least for a few rows either side of the change to a new skin.