a plastic body for use in vehicle seats , having at least one element joined therewith to form a single structural unit , which element is made from a material having different physical characteristics than those of the plastic . the element is formed as a dampening element made from a plastically deformable metal securely connected with the plastic body and / or as an insert in the plastic body . between the dampening element and / or insert and the plastic body an intermediate layer is provided , the intermediate layer being made from a material that permits relative movements between the plastic body and the dampening element and / or insert .