The present disclosure provides a seal bar. In an embodiment, the seal bar comprises a base member having a flat front surface and a flat recessed surface a distance (d) behind the front surface. The front surface defines an x-axis, X. The flat recessed surface has a first endpoint (A1), wherein an axis that is perpendicular to the flat recessed surface at the first endpoint (A1) defines a first y-axis (Y1). The seal bar has a concave surface extending the distance (d) between the first endpoint (A1) and a point (B1) on the flat front surface. The concave surface defines a quadrant arc segment of an ellipse between the first endpoint (A1) and the point (B1).