Reiter (plaintiff) brought a suit on behalf of a class of plaintiffs who had purchased hearing aids from Sonotone Corporation and five other manufacturers (Sonotone) (defendants). Reiter claimed that Sonotone had violated antitrust law by engaging in horizontal and vertical price-fixing schemes. Reiter also claimed that, as a result of Sonotone’s antitrust violations, Reiter and the rest of the class had overpaid for hearing aids at retail locations, because the prices were unlawfully fixed at higher amounts than the prices should have been. Reiter sought treble damages under § 4 of the Clayton Act. At the district court, Sonotone made a motion to dismiss Reiter’s § 4 claim, arguing that Reiter lacked standing to bring the claim because Reiter’s claimed injuries were not encompassed by § 4.