1. Prerequisites
1.1. Numerosity
1.1.1. So large that joinder under Rules 19 or 20 is impractable
1.1.1.1. Numbers
1.1.1.2. Geographic distribution
1.1.1.3. Amount at stake
1.2. Commonality
1.2.1. Common question of law or fact
1.3. Typicality
1.3.1. Of claims or defenses
1.4. Adequacy of representation
1.4.1. Of the claims of the representatives
1.4.1.1. Need to have the same stake as the class
1.4.2. Of the attorney
1.4.2.1. Competent in the substantive area of law
1.4.2.2. Experience in class actions
2. Types
2.1. (1) looks like Rule 19 grown large
2.1.1. (1)(A)
2.1.1.1. Incompatible standards of conduct
2.1.1.2. Example
2.1.1.2.1. Municipality issuing bonds
2.1.2. (1)(B)
2.1.2.1. As a practical matter, a judgment would impair or impede ability to protect interests
2.1.2.1.1. Limited fund class actions
2.1.2.1.2. Earlier actions would be dispositive of the later actions
2.2. (2) Declaratory or injunctive relief
2.3. (3) Common question class actions
2.3.1. Predominance
2.3.1.1. The questions of the class must predominate over the interest of the individuals
2.3.2. Superiority
2.3.2.1. Is the superior method to other joinder methods
2.3.2.1.1. Interest in the indvidual members to control litigation
2.3.2.1.2. Extent to which the litigation is already pending
2.3.2.1.3. How desirable is it to bring in one lawsuit
2.3.2.1.4. Management difficulties
2.3.3. Individual notice to all class members
2.3.4. Option to opt out of the litigation
2.3.4.1. Positive step