Cortland Micron Fly Line Backing is simply the toughest, smoothest and finest backing found anywhere in the world. Its unique low stretch factor eliminates the danger of building pressure on the reel. Micron's very small diameter also allows more yardage on your reel. Fish with Cortland confidence. Round braid Zero twistSmooth low-friction finishManufactured from premium Dacron fibersQty. per Pack: 1Cortland Micron Fly Line Backing is made in the U.S.A.