These wires are huge compared to stock, mainly due to the insulation. That means they withstand heat better as well as what's stated below:

409 Race-Fit Pro Wires start with Taylor's 8mm wires (available in spiral-wound or solid core) with a silicone inner insulator, fiberglass braid, and a 100 percent pure silicone jacket. Then they add a heat-treated fiberglass mesh skin and a third layer of pure silicone to get a full 10.4mm diameter. Taylor even bonds pure silicone boots directly to the wires. The results are wires that have a 100,000+ volt dielectric strength rating that gets more spark to your plugs.