Tough fish. Rocks and wicked structure. No problem. Seaguar STS Fluorocarbon is genuine 100% fluorocarbon leader material delivers incredible abrasion resistance and maximum impact and knot strength, all with a smaller line diameter than monofilament. This fast-sinking line gets you in the "strike zone" quicker, and with a lower refractive index than monofilament, it is significantly less visible underwater. Move over mono - Now you've got the optimum choice for targeting Salmon, Trout and Steelhead.