multilayer article without an axis of symmetry manufactured by compression moulding of a multilayer charge of molten thermoplastic resins , article having a feed centre corresponding to the point around which the charge is centred in the mould before compression , the distance between said feed centre and the edge of the article , known as the flow length , is variable ; characterized in that , for a given flow length , the greater the flow length , the smaller the average thickness along this length , and vice versa .