A flexible inflator provides enhanced features to an inflatable airbag restraint such as flexibility to facilitate installation in the tight spaces along the sides of a vehicle. The flexible inflator may include a housing with first and second ends made of corrugated metal. End caps are attached to each end of the cylindrical housing to form a pressure vessel. Combustible material, capable of generating inflation fluid, is positioned within a membrane inside the housing. An initiator is in communication with the combustible material, for initiating a combustible reaction within the housing. The housing is surrounded by a steel wire over-braid. The corrugated steel housing can be readily pierced without leaving a burr to damage the environmental seal. The corrugation also provides a plenum allowing gasses to readily flow from around the inflation fluid generant.