an inflatable occupant restraint device in an occupant protection system of a vehicle having at least two pieces of substantially flat inelastic plastic film having peripheral edges attached together only at their peripheral edges to form a substantially sealed airbag , an inflator coupled to the airbag and to the vehicle for inflating the airbag by providing gas to the airbag through at least one port in one of the pieces of elastic film , and an initiator for initiating the inflator in response to a crash of the vehicle . upon inflation of the airbag , the at least two pieces of inelastic plastic film deform substantially without stretching , in particular to create a shape for the airbag where the thickness is substantially smaller than the width or height and / or to provide the airbag with an ellipsoidal shape .