Howard Stern and his agent have made their shares in Sirius Satellite Radio available for sale, according to a Jan. 11 Sirius filing with the U.S. Securities and Exchange Commission.

Stern and agent Don Buchwald received 34.4 million shares of Sirius stock Jan. 9, the day Stern began broadcasting for the satellite radio provider. The stock award was triggered because Sirius hit subscriber growth targets specified in the October 2004 contract Stern signed. The company added 2.2 million subscribers in 2005, surpassing the 3 million mark.

The value of Sirius stock doubled between the time Stern signed the contract and the timing of the award. Sirius shares slipped 37 cents to close at $6.13 Jan. 11, valuing Stern’s shares at $191.6 million and Buchwald’s at $19.2 million.

The filing did not specify how much or when Stern expected to sell his shares.

Separately, Sirius announced an exclusive agreement to become standard equipment in all Rolls-Royce vehicles sold in the United States, which includes a lifetime subscription to the service.