Measuring the gap on spark plugs can be a hassle if you don?t have the right tools. With our spark plug gap gauge, the job is easy. This plug gapping tool includes both metric and SAE measurements. The front is clearly stamped with the SAE sizes, while the back is stamped with metric sizes. The measurements come in a wide range, starting at 0.020 inch (0.50 mm) and finishing at 1 inch (2.5 mm). No matter what you are measuring, our spark plug gauge will have the right size you need. All the sizes and measurement scales are easy to read, so you never have to wonder what size gap the spark plug has. This spark plug gap gauge not only accurately measures the gap size of a spark plug, but it is also able to adjust the size of the gap. Simply, place the small metal piece through the hole in the top of the spark plug gap adjuster and pull up to make the gap larger. If you need to make the gap smaller, you can just push the small metal piece onto the spark plug gapping tool. You can also use the small hole to attach the gauge to your keychain. This will allow you to always be prepared no matter what as long as you have your keys. When you need to either measure the gap in your spark plug or adjust it, use this small yet durable spark plug gauge gap tool. MEASURES METRIC AND SAE Our spark plugs gap tool is specially designed to not only display SAE measurements, but it also measures spark plug gaps in metric sizes; SAE sizes are clearly stamped on the front and metric sizes are stamped on the back WIDE RANGE This spark plug gap tool has a wide range of measurements, so that you can be sure to get the correct calculation; Our gap gauge measures spark plug gaps from 0.020 inch to 1 inch 0.50 to 2.5 mm ADJUSTER While this tool measures the gap on spark plugs, it can also work as an electrode adjuster; To widen the gap, use the small hole in the top of the coin gauge to pull the metal up; Make the gap smaller by pressing the metal against the tool ATTACHES TO KEYCHAIN The small hole also allows you to easily attach the spark plug tool to your keychain so that you always know where it is and can easily access it; Always be prepared for any spark plug measuring job with this gap gauge EASY TO READ Other spark plug gap gauges may be difficult to read; That is not the case with our spark plug gapper tool though; Both the sizes and units of measurement are clearly stamped so that you never have to wonder what the tool is reading