Berkley calls this new line the toughest monofilament in its class. It’s designed to be fished in the toughest, most abrasive environments such as around zebra mussels, oyster beds, docks and rip rap. This opaque green line is tough as iron but smooth as silk. The smooth composition of IRONSilk allows it to flow through rod guides 20 to 25 percent faster, delivering anglers longer, smoother casts. New IRONSilk is 40 percent more UV resistant than the original version.