Aspects herein relate to a medical device for providing a leak-resistant seal for use in a vascular access device. In various embodiments, a device for vascular access hemostasis is included. The device can include an enclosure configured to at least partially receive a medical device, the enclosure defining a cavity. The enclosure can have a first seal portion and a second seal portion, the cavity disposed between the first seal portion and the second seal portion. The enclosure can include the second seal portion comprising a split, septum seal. The enclosure can include a barrel in structural communication with the second seal portion. The device can include a constriction ring disposed around the barrel, the constriction ring interfacing with the second seal portion to limit movement of the split, septum seal.