TRIUMPH BSA AJS NORTON MATCHLESS ARIEL MAGNETO PRO-OU SPARK PLUG BOOTS X 2 RED. TRIUMPH BSA AJS NORTON MATCHLESS ARIEL and more. FITTING INSTRUCTIONS INFORMATION. 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.
