This universal fuel cap is compatible with many makes and models of 2-stroke and 4-stroke gas engines. The inner diameter measures approximately 1-1/4" with an 1/8" thread.
Note the plastic "fly-swatter" shaped piece which easily fits down into the tank, but prevents the cap itself from falling off or getting misplaced.
Inside Diameter: 1-1/4" (32.5 mm)
Outside Diameter: 1-3/4" (44.7 mm)
Thread Pitch: 8 (1/8" distance between threads)