United Online is planning an Initial Public Offering for its Classmates Media unit, according to a Security Exchange Commission filing.

The Monday evening filing did not disclose the number of shares being offered or expected price range but did say that the maximum offering could total $125 million.

Classmates Media, which is the parent company of Classmates.com, its flagship social networking site that boasts 50 million registered users, 2.7 of which are paid, is designed as a platform to keep schoolmates in touch. The unit also runs Mypoints.com, a loyalty marketing service for advertisers.

Woodland Hills-based United Online said that it will maintain a majority interest in the company after the IPO but did not specify the exact stake it would keep.

Classmates Media had $42 million in revenues for the most-recent quarter ended March 31, the filing said.

Shares in United Online jumped $1.26, or 9.5 percent, to $14.60 in afternoon trading Tuesday on the Nasdaq. Shares have gained more than 32 percent since Friday.