Hi big_mac,
Funny you should ask this question as I've honestly been trying to find out for years and no team I've asked thus far has been forthcoming with a straight answer. To be honest, though, they don't seem to work all that well as they fit quite tightly on the housing and still manage to rub off some of the finish.
While they're super pro-looking and all, I think the little clear stick-on tabs still work better at protecting the paint.