What is a 710?

A few days ago I was having some work done at my local garage.
A lady came in and asked for a seven-hundred-ten.

We all looked at each other and another customer asked,
"What is a seven-hundred-ten?"

She replied, "You know, the little piece in the middle of the
engine, I have lost it and need a new one."

She replied that she did not know exactly what it was, but this
piece had always been there. The mechanic gave her a piece of
paper and a pen and asked her to draw what the piece looked like.

She drew a circle and in the middle of it wrote 710. He then
took her over to another car which had its hood up and asked
"is there a 710 on this car?" She pointed and said,
"Of course, it's right there."

If you're not sure what a 710 is look at the photo below:

Now maybe you got an idea about it...Enjoy your weekend my dear friends!!!