The Von Frankenstein Monster Gear Gary Holt guitar strings are made on a U.S. workbench using the best-available, domestically sourced, raw materials. Each string in the Gary Holt Toxic Rocks Signature Set is made by hand, one at a time, with nickel-plated steel that’s carefully wrapped around a treated hex steel core. Through this meticulous process, Von Frankenstein ensures the quality, feel and durability required by the most discerning of tone aficionados.