These plugs have a designated ignition gap, heat range, and torque that works for your engine. Your original spark plug may come pre-gapped by the manufacturer. That way, you boost the efficiency of the spark plug in putting out a large enough spark to ignite the air and fuel mixture in your engine. The gapping tool will help you manually open the gap to the exact factory measurement recommended in your owner's manual. The size of the gap of a spark plug determines its firing performance. Achieve better spark plug performance.