I hope you are referring to the aerator because your spout talk is giving me a headache. Spout's don't fall off and get reattached with teflon tape. The spout is about 8" long and comes from the lever handle to the end where the water comes out. The aerator is about 3/4" across and high and screws into the end of the spout.
If your are referring to the aerator then you may be missing a part in the screens or your washer is too thin. You can buy new aerators with all the parts. Spring-Flo is excellent and will make your faucet run better than new.