Pair

Bumped into an uncle who hit my car from the front a few months back.

"Hey, kid. You know what? I hit one of your spot lights. I should only have paid for the price of one."

"Uncle, people don't sell one spot light, they sell them in pairs."

"But your car is old, you have used it before. So you should pay for the other one yourself."

"Uncle, why don't you break one of my legs and tell me you don't have to pay for it because it is so old that it has been used for 26 years?"

"Then you give me your old spot light because I paid for your new ones."

"No problem, uncle. I will give you the one you hit and the other one that you did not hit. You may have the PAIR."

...

Uncle, some things just don't come in one. 

Even a bra comes in 2 cups to make the world a better place.