A surgical access instrument for permitting access to body tissue is presented including a housing having a proximal end and a distal end, and a cannula member connected to the housing, the cannula member defining a longitudinal axis and permitting passage of a surgical object therethrough. The surgical access instrument also includes a sealing member disposed within the housing and including at least one opening therethrough, the sealing member configured to be connected to a plurality of bellows members extending in a vertical plane within the housing. The sealing member is also enabled to be displaced in a horizontal plane with respect to the longitudinal axis defined by the cannula member. Displacement of the sealing member in the horizontal plane is enabled by a roller assembly circumferentially arranged at the proximal end of the housing.