Numerosity adequate number of plaintiffs; typically requires thousands Commonality common damages and legal issues between all defendants; meaning all defendants were injured in the same way by the same entity Typicality each class member's claim must come from the same event that gave rise to the complaint, and must make the same legal argument Adequacy of Representation the representative plaintiff will adequately protect and represent the interest of the class; this means the representative plaintiff must be typical of the class Viability of Defendant although it is not a requirement of the court, it is reasonable to assume that if the accused does not have the means to compensate for the alleged damages and legal costs, it would be difficult to entice a law firm to represent the class. This is why class-actions are almost never initiated against mom-and-pop stores - it's simply not worth the law firms time to sue, since they would likely never recover enough to pay for their expenses