A surgical instrument, comprising: a housing including at least one cavity defined therein; an elongated member extending distally from the housing and defining a longitudinal axis (A-A), the elongated member configured to rotate about the longitudinal axis and including an outer shaft member defining an exterior surface of the elongated member, the outer shaft member having a proximal portion disposed within the at least one cavity; an end effector assembly coupled to a distal portion of the elongated member, the end effector assembly including a pair of opposing jaw members (30,32) moveable relative to each other to grasp tissue therebetween, at least one of the j aw members adapted to connect to an electrosurgical energy source for conducting electrosurgical energy through grasped tissue; and a stopper assembly operably coupled to the proximal portion of the outer shaft member and rotatable within the at least one cavity upon rotation of the elongated member about the longitudinal axis, the stopper assembly configured to engage at least one wall (21a,21b) defining the at least one cavity to prevent longitudinal movement of the outer shaft member along the longitudinal axis, wherein the outer shaft member is configured to provide a protruded portion which includes at least one lance (464a-c) protruding from the outer surface of the proximal portion thereof to provide a first surface and a second surface the first surface comprising a convex curved surface extending in a radial direction and the second surface comprising a flat surface extending along the radial direction, the said at least one lance forming said stopper assembly wherein the at least one cavity is defined by a distal wall and a proximal wall each defining an annular clearance configured to receive the outer shaft member therethrough and a spindle located about the outer shaft and located within the cavity with a flange disposed between the proximal wall of the cavity and the at least one lance. a housing including at least one cavity defined therein; an elongated member extending distally from the housing and defining a longitudinal axis (A-A), the elongated member configured to rotate about the longitudinal axis and including an outer shaft member defining an exterior surface of the elongated member, the outer shaft member having a proximal portion disposed within the at least one cavity; an end effector assembly coupled to a distal portion of the elongated member, the end effector assembly including a pair of opposing jaw members (30,32) moveable relative to each other to grasp tissue therebetween, at least one of the j aw members adapted to connect to an electrosurgical energy source for conducting electrosurgical energy through grasped tissue; and a stopper assembly operably coupled to the proximal portion of the outer shaft member and rotatable within the at least one cavity upon rotation of the elongated member about the longitudinal axis, the stopper assembly configured to engage at least one wall (21a,21b) defining the at least one cavity to prevent longitudinal movement of the outer shaft member along the longitudinal axis, wherein the outer shaft member is configured to provide a protruded portion which includes at least one lance (464a-c) protruding from the outer surface of the proximal portion thereof to provide a first surface and a second surface the first surface comprising a convex curved surface extending in a radial direction and the second surface comprising a flat surface extending along the radial direction, the said at least one lance forming said stopper assembly wherein the at least one cavity is defined by a distal wall and a proximal wall each defining an annular clearance configured to receive the outer shaft member therethrough and a spindle located about the outer shaft and located within the cavity with a flange disposed between the proximal wall of the cavity and the at least one lance.