The rubber washer and bushing shown in reply #3 will only provide damping in the horizontal plane and will act like a solid mount for vibrations in the vertical plane.  It will only provide the proper damping in the horizontal plane if the spacer is the correct length for the thickness of the aluminum hole  the spacer goes through.   



The rubber grommet shown in reply #9 will provide damping in all planes of motion.  It will provide the proper damping when the steel sleeve has the correct length.