Allstar Engine Spark Plug Index Tool for 14mm Spark Plug features an engine spark plug index tool. It fits 14 millimeter spark plugs and works with both flat gasket or tapered seat plugs. The spark plug index tool positions the ground strap of the spark plug properly for the best piston dome clearance. It unshrouds the electrode for a more even burn and possible gains of 5-15 horsepower. The instructions are included. It is backed by a 90-day limited factory and sold individually.