Vehicle occupant protection air bag module

An air bag module comprising:

• a retainer case installed on a vehicle body such that an open end faces a passenger compartment;
• an air bag having a stem secured to and supported by said retainer case and accommodated in a folded state therein;
• and
• an inflator provided at an end of said retainer case opposite said open end serving to issue gas into said air bag to cause inflation and deployment of said air bag;
• said retainer case including two separate parts, one being an open end side part terminating in said open end and the other being an inflator-secured end side part with said inflator secured thereto, said inflator-secured end side part being supported by said vehicle body, said open end side part being made to be less rigid than said inflator-secured end side part, wherein said open end side part of said retainer case is thinner than said inflator-secured end side part, and is thereby less rigid than said inflator-secured end side part.