They held up better than regular plug wires(so they get an extra star) but still failed. The wires and boots were fine but inside the boot melted. For something advertised as "Extreme" these don't live up to it, maybe heavy duty but that's it. I called customer service and that was a waste of time. The website states "All ignition wires have a limited one-year warranty" but the tech insisted it was a 90 day warranty. Furthermore I was told melting wasn't covered under warranty. Yes, a plug wire advertised as being able to handle "extreme" temperature is not warranted against melting. If the plug wires or boots showed damage I would probably agree with them that it was excessive heat. But both of them are spotless, only the insert in the boot was melted. To sum it up Accels "extreme" plug wires advertised as holding up to high heat won't be covered for heat damage even if they honored their 1-year warranty.