a trim element includes a base element of rigid plastic material , a supple skin , and a layer of foam , the trim element having a principle region and a marginal region . the marginal region includes an end region in which the base element has a substantially constant thickness and the layer of foam is absent , and a coupling region at a distance from the edge of the base element and the edge of the skin and in which the base element has a thickness smaller than the thickness in the end region .