<p>The rupture disks are each basically comprised of a non-metallic rupture member (12) having one or more lines of weakness (14) formed by indentations therein which define blow-out portions (16) in the rupture member. The blow-out portions are moved outwardly upon rupture of the rupture member along the lines of weakness, but remain attached to the rupture member by non-weakened portions thereof. A non-metallic reinforcing member (18) having lines of weakness (20) is attached to the rupture member for preventing tearing of the non-weakened portions of the rupture member. <IMAGE></p>