STS (Salmon, Trout and Steelhead) is the first species-specific fluorocarbon leader material targeting those speciesnDeveloped for fishing applications where strength, abrasion resistance and virtual invisibility are paramountnMaximum impact and knot strength with fast sinking line to help you reach the u0026#34;strike-zoneu0026#34; quickernSeaguar, the inventor and world leader in fluorocarbon and premium fishing line, has introduced STS, its first species-specific fluorocarbon leader material targeting Salmon, Trout and Steelhead. STS is 100% fluorocarbon leader material that 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 line, it is significantly less visible underwater.