1.Professional Spark Plug Tool: spark plug gap tool is for most of 14mm 12mm 10mm 16mm standard spark plugs. and useful for short thread depth plugs used in chainsaws, string trimmers, and other small equipment engines. NOT compatible with 18mm thread and long reach or short reach plugs spark plugs 2.Precise Distance: Dual marked stainless-steel feeler gauge with measurement range from 0.001inch to 0.04inch (0.03mm to 1mm) is made of high quality flexible 65 manganese steel, hardened and polished for long time and accurate usage. It is the preferred product in any personal or professional machinery store or automobile garage. 3.Tip: Due to the material of the spark plug, some spark plug electrodes will bounce back, which is normal for some spark plugs. You are suggested to use 0.044in feeler gauge size if your desired gap is 0.046in, smaller scale than the target gap is recommended, this automotive spark plug gap tool will meet your a plenty of applications. 4.Easy to Use: Just place your spark plug onto the spark plug gapper and then use your desired feeler, then screw the knob slowly till the side electrode compresses to the desired gap thickness. Note: This Spark Plug Gap tool will only close a gap, it will not open a gap. 5.Service: If you have any questions about the product, please contact us in time, and we will provide you with satisfactory solutions.