WASHINGTON (Dow Jones/AP) ? Bermuda-based RAM Holdings Ltd. is planning an initial public offering to sell up to $250 million in common stock, according to a filing on Friday with the Securities and Exchange Commission.

Details about the number of shares being offered and estimated price range for the IPO weren't disclosed in the filing. Some of the shares will be offered by certain shareholders.

RAM Holdings is a Bermuda-based provider of financial guaranty reinsurance.

The company said it plans to use net proceeds from the IPO to increase capital and surplus of its wholly-owned unit, RAM Reinsurance Co. It won't receive any proceeds from the sale of the shares by the shareholders.

Banc of America Securities LLC, Merrill Lynch, Pierce, Fenner & Smith Inc. and Keefe, Bruyette & Woods were listed as the underwriters for the offering.

For the nine months ended September 30, 2005, RAM Holdings reported net income of $14.5 million, down from $19.8 million it reported for the same period in the prior year.

The $250 million valuation for the IPO was estimated solely for calculating the registration fee, the filing said. Often, the eventual price terms of an IPO differ substantially from the valuation in the first registration.

RAM Re, which carries a AAA rating, was formed in 1998 to take advantage of an increased emphasis on diversity of reinsurance sources by the "AAA/Aaa" rated financial guaranty primary insurers.

Since then it has conducted at least three rounds of private equity funding, with the last one reported occurring in 2003.

Its shareholders include The PMI Group, Inc. Transatlantic Reinsurance Company, CIVC Partners, L.P., and MBIA Insurance Corporation.MBIA, a new shareholder and key customer of RAM Re, is the largest triple-A rated monoline financial guaranty insurance company.The company has had strong relationships with each of the four largest primaries and is developing relationships with the newer entrants in this market.

Other investors have included : GSC Partners, High Ridge Capital Partners L.P., Canaan Equity, L.P., Western General Insurance Company, and the Bank of Bermuda.