I run the Jacobs 8.5mm with ceramic 90 degree ends. I'm running the hedman headers with the air log and have had troubles with the routing around cylinder 5. Jacobs has a lifetime replacement policy that I've tested 7-10 times. All related to the same cylinder:-| Anyway, call them day one and a new wire arrives in a couple of days. The wires are run less than 100 ohms resistance, allowing a larger gap at the business end. I'm happy....