The inner sel is held tight on the inner drum with a long spring seated in a deep groove in the rubber.
The outer seal is held by a wire hoops with a shorter spring to hold the tension.
Believe it or not you just peel it over the lips and pull it.
I've just removed mine as it was torn. I've got a new one and now I can't fathom how to get it back on!
The washing is piling up!!!
Tim Wilson, July 2006