To fit a camel

Another condom joke. Source unknown...

***

A grandfather is visiting his grandson at college. On the table he sees a box of condoms but he doesn't know what they are for. He decides to ask his grandson.

"Grandpa, those are condoms, they're rubber sacks that you use to keep your cigarettes dry" the boy says, too embarrassed to tell his grandfather what they really are.

The next day, the grandfather goes to a pharmacy. "I'd like a box of condoms" he says.

The pharmacist asks if he would like any particular kind. He replies "Big enough to fit a camel".