An air bag having a first monolithic layer and a second monolithic layer, said first and second monolithic layer being attached to each other along a closed line such that the surface area of the first monolithic layer within the closed line is larger than the surface area of the second monolithic layer within said closed line. The first monolithic layer and the second monolithic layer define a fluid chamber bounded by said closed line, wherein the first monolithic layer rests on the second monolithic layer, and is of an at least substantially corrugated shape when said fluid chamber is deflated. The air bag also includes at least one fluid port in fluid communication with the fluid chamber.