Top helmet maker Riddell, already defending mass litigation by ex-NFL players, now faces a putative class action over ads that claimed its products helped stifle concussions.

The plaintiffs in Thiel v. Riddell Inc., filed Wednesday in federal court in Camden, allege the Rosemont, Ill., company used shoddy science to justify claims that its Revolution helmet boasted “concussion reduction technology” and reduced injury risks by 31 percent.