What’s a 710?

Yesterday I was having some work done at the car dealer.  A blonde woman came in and asked for a seven-hundred-ten.

They all looked at each other, and the mechanic asked, “What is a seven-hundred-ten?”

She replied, “You know, the little piece in the middle of the engine.  I lost it and need a new one.  It had always been there.”

The mechanic gave the woman 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 the hood up and asked, “Is there a 710 on this car?”  She pointed and said, “Of course, it’s right there.”

Do not have anything in your mouth when you click the link!  What was the mysterious 710?