Mont. Code Ann. § 35-14-804

If the articles of incorporation or action by the board of directors pursuant to 35-14-602 authorizes dividing the shares into classes or series, the articles of incorporation may also authorize the election of all or a specified number of directors by the holders of one or more authorized classes or series of shares. A class or series or multiple classes or series of shares entitled to elect one or more directors constitute a separate voting group for purposes of the election of directors.