RIO Dacron Fly Line Backing - RIO's traditional Dacron braided backing features high strength and low stretch and is unsurpassed in quality. A good compromise between thinness and the ability to make blind splice loops. It's easier to knot than other brands that are very thin but have too tight a weave for a blind splice loop. A HIGH QUALITY, SUPER SMOOTH BRAID that is 100% reliable Braided backing