What gift does Della buy for her husband in "The Gift of the Magi"?

In O. Henry's classic short story "The Gift of the Magi," Della buys her husband, Jim, a platinum fob chain for his pocket watch. In return, he buys her a set of tortoise shell combs.

However, in an instance of situational irony, Jim has sold his watch in order to pay for the combs, and Della has sold her hair to pay for the fob chain. At the end of the tale, the author uses this irony to make a larger point about generosity. Because they sold the items that were most precious to them in order to please someone else, "of all who give gifts these two were the wisest."