Abstract: A annular gasket defining a circumferential extension trajectory lying on a main plane, a section plane normal to the extension trajectory and to the main plane, and sagittal plane tangent to the extension trajectory and normal to the main plane, and including a profile defining on the section plane an X shape divided by the sagittal plane in a first side and a second side, in which the first side is divided from the main plane into a first lip suitable for being inserted in a seat and a second lip, the second side is divided by the main plane into a third lip and a fourth lip, and the first lip is rounded and normally extends to the sagittal plane less than the second lip, and the second lip defines a free end including an edge.

Abstract: A seat comprising a first eyelet secured to the top of the seatback, on one side of the same, and inside which a first belt slides; a winding device for the first belt, secured to the rear surface of the seat; a carriage traveling substantially longitudinally and to which is secured one end of the first belt; a second eyelet secured to the seat portion of the seat and inside which a second belt slides; a second winding device secured underneath the seat for winding the second belt; and means for retaining one end of the second belt, which means are secured to the seat for enabling the connection of connecting means to which the end of the second belt is secured.