The invention relates to a method of manufacturing a catheter, wherein the catheter comprises an elongate portion having a proximal end and at least one lumen at said proximal end, at least one extension tube having a passage, and a coupling element, the distal portion of the extension tube being capable of communicating with a lumen of the elongate portion via a passage in the coupling element wherein the method comprises a step wherein a removable insert element locates and holds the extension tube in contact with the elongate portion during the manufacture of a coupling element. The invention also relates to a removable insert for use in the manufacturing of catheters.