| 摘要 |
It is an object to reduce eccentricity between a terminal nut and an insulator. A spark plug includes an insulator, a terminal nut, and a metallic shell. The outside diameter of the insulator at a rear end of the metallic shell is smaller than or equal to 8 mm, and the contact area between a flat portion of the insulator and a contact surface of the terminal nut is smaller than 10 mm 2 . |
