It's a type of braid used for fishing, I use it as a mainline for my river feeder fishing, compared to regular mono it's very low diameter for its breaking strain and has zero stretch, basically it lowers the resistance of the line against the flow of the water meaning lighter tackle can be used and it gives better bite detection, the 4lb test I use is the same or lower diameter than 1lb test mono, I've none spare though I'm afraid. If you want a low stretch, low diameter cord, could always use dental floss.