An improved heat exchanger is disclosed. The heat exchanger is of the type including a pair of headers and a plurality of tubes extending between and fluidly connecting the headers. The improvement comprises a tubular structure for and defining in part each of said headers. The tubular structure is defined by a pair of body elements and has opposed longitudinal joints defined by overlapping portions of the body elements. One of the body elements overlaps the other of the body elements to define one of the joints and is overlapped by the other of the body elements to define the other of the joints.