A sheath assembly (26B) comprising a sheath body (40B) comprising a generally flexible tubular structure, a proximal end, and a distal end, the sheath body defining a longitudinal axis； a hub (42B) coupled with the proximal end of the sheath body, the sheath body and the hub having aligned openings forming a passage therethrough； and a valve comprising an annular member disposed against a surface of the hub facing the sheath body, the annular member having and opening therethrough disposed in the passage； and a sealing member (240) having an engagement portion (242) coupled with a structure of the sheath assembly disposed generally between the surface of the hub and the distal end of the sheath body, and a seal portion (243) projecting into sealing engagement with the opening in the annular member in a sealing position and disposed away from the opening in the annular member in an open position.
