An end effector for a robotic-assisted surgical system having an adjustable inner diameter. In embodiments, the end effector includes a main body having an opening extending through the main body, one or more members located within the main body that extend into and retract from the opening to vary a diameter of the opening through which a tool may be inserted, and an adjustment mechanism on the end effector and coupled to the one or more members for varying the diameter of the opening.
