with an inner flange portion of the peripheral wall 13b of the outer covering 13.
In the air bag module 1, a fastening bolt 15 of the retainer 11 installed in the interior of the air bag 12 penetrates through the air bag 12 and projects out of the air bag case through a through-hole of the inner plate 14. The air bag module 1 is fastened to the side plate 3 of the seat back frame 2 by the fastening bolt 15 and a nut.
When the air bag module is to be installed in the side of the seat back, the air bag module is preferably installed in the cavity formed in the side of the back pad, by using a box-like holder having an opening. When thethe side plate through the holder, whereby the air bag module is installed in the side of the seat back;
the holder further including flange portions, and at least first and second brittle sections serving as breaking portions;
the peripheral wall comprising a front side wall section which is to be faced to a front side of the seat back, a rear side wall section which is to be faced to a rear side of the seat back, an upper side wall section, and a lower side wall section;
the flange portions projecting outwardly from edges of the front, rear, upper and lower side wall sections;
at least a flange portion of the front side wall section having a thin metal plate embedded in an inner surface thereof and mounted thereto, whereby