Cortland Micron is the standard by which all fly line backing has been judged for more than 50 years. World famous for its tight, round braid, smooth low-friction finish and stretch-resistant performance, Micron is manufactured from premium Dacron fibers. 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. Available in 20-lb. and 30-lb. test.