Fluorocarbon
Also called fluoro, FC line
Single-strand line made from a dense polymer that refracts light almost like water, so it is much harder for fish to see.
Fluorocarbon's selling point is invisibility. Its refractive index is close to that of water, so a fluoro leader disappears far better than nylon in clear conditions. It is also denser than water, so it sinks, and it resists abrasion better than mono, which matters when your line is dragging over rock and shell.
It stretches less than mono but more than braid, which puts it in a useful middle ground: enough sensitivity to feel a jig ticking bottom, enough give not to tear hooks out. The sinking behavior makes it wrong for topwater, where you want line floating on the surface, and right for anything worked along the bottom.
The catch is handling. Fluoro is stiff and has more memory than mono, so it comes off the spool in coils and it punishes a sloppy knot. Wet every knot before you cinch it or the friction will weaken the line at exactly the point that matters.
Most anglers use fluorocarbon as a leader off braid rather than filling a whole spool with it. That gets the invisibility without the handling problems.
Common questions
When should I use fluorocarbon instead of monofilament?
In clear water, on bottom contact baits like jigs and Texas rigs, and anywhere line is scraping rock or wood. Use mono instead for topwater and treble-hook baits, since fluorocarbon sinks.
Related terms
Where this comes up
The guides that use fluorocarbon and show it on real gear.
Fluorocarbon is one of 206 terms in the glossary.
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