A microdebrider comprising: (a) a handpiece； (b) an interchangeable tip connected to the handpiece； (c) an outer tube rotatably connected to the interchangeable tip, the outer tube including an outer tube window； (d) an inner tube extending at least partially through the outer tube, the inner tube including an inner tube window； (e) a lock selector connected to the inner tube； and (f) a bias device； wherein the bias device is movable, and upon movement of the bias device into contact with the lock selector the inner tube is immobilized so that the inner tube window is aligned with the outer tube window, aligned with a wall of the outer tube, or in a condition therebetween.
