An inflatable restraint device for fastening to a seat of a vehicle includes at least one inflatable cushion with an outer surface and a plurality of tethers. Each tether includes a first end and a second end. The tethers are fastened at the first ends to the outer surface of the cushion and the second ends of the tethers are designed to be fastened to a seat. The tethers are designed to be releasably fastened on at least one of the ends.