A header for an implantable medical device, the header comprising: a header body comprising molding material and at least one component within the molding material; and an attachment plate configured to couple the header to a body of the implantable medical device, wherein the attachment plate comprises: a base configured to be mechanically coupled to the body of the implantable medical device, wherein the base defines a space configured to receive at least one feedthrough wire from the body of the implantable medical device, the at least one feedthrough wire configured to be coupled to the at least one component of the header body; and characterised by at least one extension extending from the base of the attachment plate, wherein the at least one extension defines at least one void configured to receive a portion of the molding material to couple the attachment plate to the header body, wherein the at least one extension is substantially embedded within the molding material, wherein a portion of the molding material is within the void(s) such that the attachment plate is mechanically coupled to the header body, and wherein the base is of metal and a portion of the base is free of the molding material, to facilitate mechanically coupling the header to the body of an implantable medical device by welding the metal base to a metal housing of the body of the implantable medical device. a header body comprising molding material and at least one component within the molding material; and an attachment plate configured to couple the header to a body of the implantable medical device, wherein the attachment plate comprises: a base configured to be mechanically coupled to the body of the implantable medical device, wherein the base defines a space configured to receive at least one feedthrough wire from the body of the implantable medical device, the at least one feedthrough wire configured to be coupled to the at least one component of the header body; and characterised by at least one extension extending from the base of the attachment plate, wherein the at least one extension defines at least one void configured to receive a portion of the molding material to couple the attachment plate to the header body, wherein the at least one extension is substantially embedded within the molding material, wherein a portion of the molding material is within the void(s) such that the attachment plate is mechanically coupled to the header body, and wherein the base is of metal and a portion of the base is free of the molding material, to facilitate mechanically coupling the header to the body of an implantable medical device by welding the metal base to a metal housing of the body of the implantable medical device. a base configured to be mechanically coupled to the body of the implantable medical device, wherein the base defines a space configured to receive at least one feedthrough wire from the body of the implantable medical device, the at least one feedthrough wire configured to be coupled to the at least one component of the header body; and characterised by at least one extension extending from the base of the attachment plate, wherein the at least one extension defines at least one void configured to receive a portion of the molding material to couple the attachment plate to the header body, wherein the at least one extension is substantially embedded within the molding material, wherein a portion of the molding material is within the void(s) such that the attachment plate is mechanically coupled to the header body, and wherein the base is of metal and a portion of the base is free of the molding material, to facilitate mechanically coupling the header to the body of an implantable medical device by welding the metal base to a metal housing of the body of the implantable medical device.