This is a 15 inch panel wire that is used to make the jump between panels if you are using a zig-zag configuration, or if you need a little extra cable to get from your controlling mechanism to the first panel in a daisy chain.
A typical use case scenario is pictured here as a depiction of 6 panels being daisy chained and zig-zagged off of one port of an Octoscroller or Pi Hat. The red lines represent the short wires that are included with each panel purchase. The green lines represent this product. They allow you to jump from one long run to another.