I have the Total Enclosure System (TES), it has a bottom part that you ride onto then cover the bike and zip it together, stops it being blown away in our lovely weather.
So far it's been a year and its still waterproof and the zips still work.
Only problem is I have the largest size and with the Givi screen and top box on, you can't fully zip it up, plenty to stop it blowing off, about half way. So for the winter, when not riding for a while, I take the box off and lower screen and it fits perfectly.