ACCEL's improved copper core spark plugs have a conventional ground electrode which is designed to unshroud the center electrode which helps the spark for a better ignition. This allows the flame to expand more rapidly in the chamber which helps in producing more horsepower and reduces misfire. Improves throttle response, fuel economy and less fouling. Purified alumina insulator prevents arcing. Machine rolled threads protect heads. Shorty configuration is 3/16 inch to 3/8 inch shorter depending on the application to gain critical air gap space between the spark plug boot and the exhaust manifold or header tube. This helps eliminate burning the spark plug boot or dimpling the header tube. The shorter spark plug length also can make it easier to install and remove the spark plugs in certain applications where there is not a lot of room to fit a socket or move a wrench around.