This professional heavy-duty spark plug gap setting tool is completely portable for field use, yet precise enough to set gaps to within 0.001". The precision screw drive with its comfortable knurled knob gaps any type of Massive Electrode Aviation Spark Plug reliably and without any danger of damaging the spark plug. Simply screw the spark plug into the base of the tool and turn the knob to the required gap width. Complete kit includes ATS420 Gapping Tool plus ATS450 wire feeler gauge. 1 lbs (0.5Kg) shipping weight.