Exhaust Manifold Flange Nuts have a wide flange at one end of the nut, which acts as an integrated washer. By definition, a flange could either be an external or an internal ridge or rim that has been added to provide strength and acts as an attachment to another object. The pressure that occurs over the part of the Exhaust Flange Nuts being secured is distributed, which in turn reduces the chance of damage to the nut.