Abstract: A method for the manufacture of a heat fusion fining, which comprises i) forming a body (1) comprising at least a first layer of a first cross-linked polymeric material, ii) embedding or partly embedding a ferromagnetic heating element (11, 12) in a second polymeric material (13, 14) to form an insert (7, 8), the ferromagnetic heating element (11, 12) having a Curie temperature equal to or greater than the crystalline melting point or softening point of the second polymeric material (13, 14), and iii) assembling the body and the insert (7, 8) to form the fitting.