High quality Japanese made 100% PVDF fluorocarbon line. It's refraction coefficient of light is the same as water, therefore FANTOM line is virtually invisible in water. It sinks  four times faster. It does not absorb water, so it keeps its characteristics even after being under water for a long time. It is highly resistive to abrasion on shells, rocks or teeth. It is indispensable in use as a leader for predatory fishing. It showed great results when we used it when carp fishing for large and cautious fish.