Seal assemblies or valves, generally for use in trocar assemblies, are provided for reducing the amount of contact between an instrument being passed into and out of a trocar assembly and an inner surface of a sealing wall of such seal assemblies or valves. In one exemplary embodiment a valve includes an activation extension that is formed on the inner surface of the sealing wall of the valve and is configured such that a distal end of the sealing wall is moved to the open position by an instrument contacting the activation extension. In one embodiment the instrument does not come into contact with the inner surface of the sealing wall during the procedure. In another embodiment a distal-most end of the activation extension can be closer to a longitudinal axis extending through the flange than the inner surface of the sealing wall.