Abstract: An integral reverse buckling fluid pressure rupturable apparatus comprised of a support body formed of a ductile material having opposite ends and having a recess extending inwardly from one of the opposite ends, the internal terminus of the recess being positioned in close proximity to the other of the opposite ends of the body or to the terminus of another recess extending inwardly from the other of the opposite ends, whereby a relatively thin integral rupturable portion is formed in the body. The rupturable portion is of a concave-convex shape formed by applying pressure on a side of the rupturable portion when in a substantially flat state.