An airbag having an outer skin having an inner side and an outer side is described. The outer skin has an inflator attachment region in which an opening structure for an inflator is provided. The airbag is a part of an airbag assembly further having a flange and an inflator extending through the opening structure and being attached to the flange. In order to provide the possibility of an easy and automatable mounting process, the opening structure having at least two basically radially extending cut-outs, so that the attachment region has at least two flap sections being separated by the cut-outs. These flap sections can be pulled apart during the mounting process, such that the inflator can be attached to the flange.