Cortland Micron is the standard by which all fly line backing has been judged for over 50 years. World-famous for its tight, round braid, smooth low-friction finish, and stretch-resistant performance, Micron is manufactured from premium Dacron fibers in our New York facility. Unlike looser, flat braids, Micron comes with zero twist, is virtually tangle-free and knots perfectly every time. Ask any fly angler who sees their backing more than most, and they'll tell you they use Micron — every time.