Loop-to-loop connection to backing (orange Micron) enables easy and fast change of flyline.

Fly line backing is typically an afterthought for Florida fly fishers who fish for bass or bream or smaller saltwater species that rarely take much fly line off a reel once hooked. But backing is a major consideration when tarpon, billfish, bonefish, bull reds, big snook or other brutes are targeted.

Traditionally, polyester Dacron and Micron gets the nod, either 20-pound-test or 30-pound depending on fly tackle class. But gel spun polyethylene (GSP, or braid) has its devotees, as well as advantages and drawbacks.

The major advantage of GSP is extra capacity on your spool thanks to super small diameter. Figure on gaining at least 60 percent spool capacity when you switch from thicker Micron or Dacron to GSP. UnlikeDacron, which stretches around 10 percent under pressure, GSP stretches very little. And that means minimal shock absorption—a decided disadvantage and something of a warning to fly fishers playing big or jumpy fish on light class tippets.

GSP certainly shines in the strength department—much stronger than Dacron of similar diameter. If you switch from, say, 30-pound-test Dacron to 30-pound GSP, you will discover your reel spool now holds more than twice the yardage. But that thin stuff can also be a nightmare should you not pack it on the spool tightly as you reel in a big fish. GSP can dig into underlying wraps and that can cause a jam that can pop your tippet should a fish run the line off again, a function of not only small diameter but coating slickness, too. Reportedly, the newer GSPs with a round profile don’t dig in as readily. It would be wise to go with heavier GSP, for example, 50-pound-test rather than 20 or 30 to further decrease the chances of it happening, too.

Another GSP drawback: cut fingers while guiding it onto the spool under pressure. Big game fly fishers might consider doing a Michael Jackson impersonation, wearing a glove on their rod hand while reeling GSP onto the spool during a big-fish battle. Bring it back in a criss-cross pattern to decrease the chances of it jamming in the spool.

Speaking of epic battles, keep in mind that GSP has lower water friction—it cuts through the water and unlike Dacron does not create that troublesome “belly” between the rodtip and a fish that is 100 yards or more from you, is running perpendicular to you, or does a course change repeatedly.

If you fish around structure such as rough bridge pilings or on tidal flats with lots of rocky outcroppings or sea fans, GSP backing is more abrasion resistant than standard Dacron. That’s a consideration should you hook fish that run hard and long over rough country.

The fear of GSP’s wear on fly rod guides has waned for the most part—modern guides on most quality fly rods are hardened, and stand up to the stuff.

If you choose to spool up with GSP, it is slick, so first wind on enough Dacron or Micron to cover the spool arbor and tie your GSP to that before filling up. GSP can slip on the arbor—the while “cylinder” of backing can spin on the spool under pressure.

Should you stick with good ol’ Dacron, you’ll enjoy the lower price, great knot strength and integrity, and you will not need that Michael Jackson glove. FS

The following manufacturers offer both Dacron and GSP backing.


Micron (Dacron) – 20-and 30-pound-test on 100-to 2,500-yard spools. Price range $11.95 to $141.90.

Fair Play Micron – 20-and 30-pound-test on 100-and 250-yard spools. Price range $7.95 to $23.90.

GSP – round shape, available in 30-, 50-and 80-pound-test on 300-and 2,500-yard spools. Hi-vis yellow, hi-vis orange, white, blue, hot-pink; $37.95 for 300 yards.

Scientific Anglers

Dacron – 20-and 30-pound-test on 100-to 5,000-yard spools; price range $8.95 to $179.

XTS GSP Backing — 30-and 50-pound-test on 100-to 3,000-yard spools. Price range is $12.95 to $499.

The Orvis Company

Braided Dacron Backing – 20-and 30-pound test on 50- to 2,500 yard spools. Price range $4.95 to $130.

GSP Backing – 35-and 50-pound- test on 100-to 1,200-yard spools. Price range $12 to $195.

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