Check the listing for details. BLACK 8MM PERFORMANCE IGNITION LEADS HARLEY DAVIDSON LEADS ARE 11" LONG TO ORDER. Color: Black, Condition: New other (see details), Made in United Kingdom. Listed at 56.29 USD. The ignition leads deliver high performance over a wide temperature range. They have a waterproof seal around the spark plug and are resistant to oil, water and under-bonnet corrosive materials.Ignition leads connect the distributor to the spark plugs and therefore form an important part of the overall car engine ignition system. Ignition leads or cables carry the High Tension Voltage from the ignition coil that is required for the spark plugs to ignite the air/fuel mixture. It's important that the HT Voltage is not allowed to escape before reaching the spark plugs. Faulty ignition leads, due to perished, torn or chaffed cable insulation and dirty cable connectors are common causes of rough running, misfires, high fuel consumption and MOT emissions failures. FITTING INSTRUCTIONS INFORMATIO.