What size?

A man walked into a dress shop and told the clerk he wanted to buy a surprise formal evening gown (礼服, 睡袍)for his wife. 

"What size?" asked the clerk.

The man shrugged blankly.

Trying to help, the clerk inquired, "Well then, what are your wife's measurements?"

The man thought for a moment. "Small, medium, and large and in that order."