It’s a gas cap!
2 months ago
It works exactly as advertised. You stick it in the filler pipe for the fuel tank, then turn it clockwise until it stops. Turn just a tad bit more and it will click, indicating it is in the proper position to seal and vent. If you need to remove this cap, to add more fuel to your tank, simple turn it counter clockwise.
What kind of vehicle do you drive? 1998 Honda Civic