The Cokin Adapter Ring is made of a very durable metal which permits the user to screw it onto the front camera lens without concern of stripped threads. No need for concern about filters or filter holders "accidentally" falling off unexpectedly.
I really enjoy using the Cokin P filter system. I bought the extra rings so I don't have to keep changing them between lenses. I like that they make lens covers that snap on to the rings making it quick and easy to start shooting photographs.