A cap including an outer shell configured to be coupled to an access port of an endoscope, and a resilient member positioned interior of the inner peripheral surface of the outer shell. The resilient member includes an upper surface, a lower surface, an outer peripheral surface and a central opening sized to accommodate an endoscopic instrument therethrough. The resilient member further includes a slit extending outward from the circumferential surface of the central opening toward the outer peripheral surface of the resilient member.