It purchased for the purpose of measuring the rotation speed of a four-stroke single cylinder engine. The description of the item stated that it is "compatible with 2 stroke 1, 2 cylinder, 4 stroke 1, 2, 4 cylinders", so purchasing this product, the general 4-stroke single cylinder (2 Rotating 1 ignition) was not supported. There was a note at the bottom of the item description, but it was overlooked. In the description of the box of goods, there is a sentence with the meaning of "It corresponds to 4 strokes 2, 4 cylinders and 4 stroke 1 cylinder with 1 rotation per ignition". Since most 4-stroke engines are 2 revolutions per 1 firing, I feel that the way of writing the item description field is inappropriate. Since I wanted to use it earlier this time, I decided to estimate the number of revolutions from the number of fires.