A header for a heat exchanger having spaced manifolds and tubes extending between the manifolds is disclosed. The header plate comprises a header plate forming a portion of the manifold and having an outward surface for orienting away from the interior of the manifold. At least one opening is formed in the header plate, and is elongated with a longitudinal axis and opposite ends. The at least one opening has a perimeter with sides and ends. A ferrule extends from the outward surface of the header plate along portions of the perimeter of the opening. The ferrule includes at least two ferrule portions formed along portions of the perimeter of the opening. The ferrule is absent from portions of the perimeter of the opening between the portions of the perimeter having the ferrule portions formed thereon.