Your choice 50 or 100 yds. Cortland Micron 20 - lb. Fly Line Backing. Tough, smooth, and hugely popular! Cortland"s classic Backing has been improved with technically advanced braiders and high-pressure color drying. Available in spool of 50 or 100 yds. State Length. Order Now! Cortland Micron 20-lb. Fly Line Backing