A complete spark plug gapping solution for field or bench use includes our ATS420 Heavy Duty Spark Plug Gapping Tool to accurately set your spark plug gaps to within 0.001". You also get a set of wire feeler gauges (p/n ATS450) to verify gap size. If you should happen to accidentally over-gap the plug, then the included Gap Expansion Tool (p/n ATS483) will get you back on track. And finally, we've included an Electrode Erosion Gauge (p/n ATS482) to make sure that your gapped plugs are still in serviceable condition.