100 Fluorocarbon LeadernDSF - Double Structure FluorocarbonnBest Tensile StrengthnAmericau0026#39;s # 1 LeadernLeast StretchnIncredible Impact and Abrasion Resistance. Fast Sinking, Superior Tensile and Knot Strength. Seaguar Blue Label 100% Fluorocarbon Leader is preferred by anglers all over the world.