The top of the spark plug nut is hexagonal, 16, 18 and 21MM respectively Material: The spark plug wrench is made of high-quality high-carbon steel, which is stable and can be used for a long time. Usage: This spark plug wrench is suitable for automobile workshops, agricultural machinery workshops or small household appliance workshops. 720 degrees of adjustment: easily install and remove spark plugs, even in tight spaces Note: The universal spark plug wrench will lose oil if used for a long time. It is recommended to check and clean the spark plugs frequently. Note: The data are all measured manually, please allow an error of 1-3 cm due to differences in light and display, there may be some color differences, please refer to the actual item received.