Fluorocarbon line is made from polymer of fluorine bonded to carbon. This super line has several advantages over monofilament. This line comes the closest to the refractive index of water so it is virtually invisible under water. The invisibility is needed in clear waters. This line has ultra low stretch and your hook sets are positive. It is much more resistant to abrasion. It doesn’t float and allows your lures or bait to fall faster and deeper quicker. This line doesn’t absorb water like monofilaments and this makes it much stronger. Many top hooks crank their fluro leaders tight on a stationary object and let them stretch to remove any memory in that the line acquired during storage before deploying their baits. This causes he fluoro leader to lay straight. Fluorocarbon isn’t an option for live baiting giant tuna, it is a necessity.