Page 24 - Joseph B. Healy "The Pocket Guide to Fishing Knots"

The next in the troika of today’s popular fishing-line materials is

fluorocarbon (polyvinylidene fluoride). Fluoro is only used as leader
material because it’s expensive—more expensive than mono, for sure—
and it holds memory when coiled, so it is most manageable in shorter
pieces when coiling isn’t an issue. The same as mono, it’s extruded as a
single piece. It actually has greater translucence than monofilament and
is therefore less visible to fish underwater.

The Orvis Company makes a popular fluorocarbon leader and tippet material called Mirage.

This is because fluoro has a similar refractive index to water so light
passes through it. And so, because these lines are not as visible to fish,
anglers can use heavier pound-test fluoro lines in fishing situations. It’s

also stiffer than mono, which helps casting, particularly the presentation
fly cast when you’re dropping the fly—the fluoro straightens out nicely as
it unfurls. It absorbs no water so doesn’t “weaken” while being fished, and
actually sinks faster than mono and is more resistant to abrasion. It
doesn’t “stretch” or give as quickly as mono does, but that can play