Parts are provided which combine structural reinforcement of hollow profiles and light weight means of attachment. Optionally, the part may also provide an acoustic baffle. The parts consists of a core coated with expandable structural reinforcing foam on at least part of its surface the core being provided with means for receipt of a nut and means to prevent rotation of the nut. Optionally, a piece of a second expandable material is provided on at least one extremity which can expand to fill the entire cross section of the hollow profile. In a preferred embodiment, the hollow profile is the A, B or C pillar of a vehicle and the nut is used for attaching doors.