Best Fly Line Backing: The Insurance Under Your Fly Line

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Backing spends most of its life doing nothing, then decides everything the day a strong fish empties your fly line. It also fills the spool so your line sits on a larger arbor and picks up faster. The choice is between dacron, which is cheap, easy to knot, and standard for trout, and gel-spun polyethylene, which packs far more capacity and strength at the same diameter but costs more and demands care with knots and fingers. We weighed strength ratings, diameter and resulting reel capacity, knot behavior, color options for tracking a running fish, and rot resistance. Twenty-pound dacron covers nearly all freshwater fishing and most anglers should not overthink it. Thirty-pound dacron or gel-spun suits saltwater, spey setups, and small reels that need more capacity than their size suggests. Replace backing when it fades and feels fuzzy, not after a decade of guessing.