What’s a seven-ten cap?

A lady went to an auto-parts store and asked for a seven-ten cap. All the clerks looked at each other, and one said, “What’s a seven-ten cap?”

She said, “You know, it’s right on the engine. Mine got lost somehow and I need a new one.”

“What kind of a car is it on?” the clerk asked.

“My 2000 Toyota,” she replied.

“Well, how big is it?”

She made a circle with her hands about three-and-a-half inches in diameter.

The clerk asked, “What does it do?”

“I don’t know, but it’s always been there.”

At this point, the manager came over. He handed her a notepad and asked her if she could draw a picture of it. The customer carefully drew a circle about three-and-a-half inches in diameter. In the center she writes, “710.”

The manager, looking at the drawing upside down, walked to a shelf and grabbed an OIL cap.