A fitting (1) of weldable, thermoplastic material of a modular structure, comprising a number of elements (2, 3, 9, 10, 11, 12), at least one main element (2, 9) and at least one connecting element (3, 10, 11, 12), characterized in that the elements (2, 3, 9, 10, 11, 12) have end faces (4, 5) at right angles to the center axis (8), and the elements (2, 3, 9, 10, 11, 12) are welded to one another exclusively at the end faces (4, 5).