An IBOP is a “dart” type pressure sealing device that has a conical head which mates to a conical negative sealing surface. This design allows for one-way pressure containment. M&M offers two variations of “dart type” inside blow-out preventers (IBOPs). The traditional style is two-piece and is similar in construction to other dart type IBOPs. Recognizing the need to reduce as many internal connections as possible we have also developed a one piece IBOP.