I sometimes use them in screw necked bottles.
They are often a very tight fit in previously corked bottles and you will need to hammer them home with a rubber mallet and then use a knife to lever or pipe spanner to get them out again.
The inside diameter of screw necked bottles varies considerably. Sometimes the plastic stoppers are a good fit, sometimes they are a loose fit and the bottles must be stored upright, and sometimes the stoppers don't even touch the sides at all. If I don't have the screw cap then I always test the fit of a plastic stopper before I bother trying to remove the label.
Now I have some of bobsbeer's Novatwist caps, this isn't such an issue, but they are cheap and re-usable.