In Carrera v. Bayer Corp., 727 F.3d 300 (3d Cir. 2013), the Third Circuit applied its prior decisions requiring that a class certified under Rule 23(b)(3) be “ascertainable.”  The Carrera court found a class could not be certified where the purchasers of the defendants’ products could not be ascertained in an administratively feasible manner.  Plaintiffs moved for rehearing en banc, which the Third Circuit denied.  Carrera v. Bayer Corp., No. 12-2621 (3d Cir. May 2, 2014).  Four judges dissented from the denial of rehearing en banc, including the author of Marcus v. BMW of North America, LLC, 687 F.3d 583 (3rd Cir. 2012), a leading Third Circuit ascertainability opinion.  The dissenting judges stated that Carrera went too far, threatening the viability of consumer class actions.  They opined that the ascertainability requirement, which is judicially created, should be flexible in its application, especially where the defendant’s conduct and business practices make the class difficult to ascertain.