Description: Universal Fitment: Compatible with most 10mm 12mm 14mm 16mm spark plugs Precise operation: The spark plug gapping tool will give a gap every time Installation: 1. Simply place the spark plug into the gapping tool. Use the desired size of the gap thickness sensor. 3.Turn the knob with the gap sensor in place until the side compresses to the desired gap thickness. No more random plug surface to close, then use the coin slot, opening it back, do it once with precision using our Stainless Steel Metal tool surface: oil coated ruler surface stainless steel Specification: Main material: aluminum alloy Size chart: 12.2cm/4.80 inch Package include: 1 piece spark plug gapping tool Note: Please allow slight errors due to manual measurement and different monitors.