The backing is more of a reel filler than insurance against a long running fish. I can't remember the last time I was into the backing on a trout.

You want the spool filled with enough backing to have your fly line fill the reel to the end. This helps keep your fly line to the largest coil possible on the reel and eliminates the small coils that will kink up your fly line and make it annoying when you strip line off the reel...


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