It has been getting harder and harder to find out what that rating is. I have been lied to by sales reps more than once about this. I don't know about Oakly, but if you take the trouble to find out, (and I think you should)when you talk with some one, If they don't know what you are talking about, don't try to explain it, just ask for some one else (a tech person) and get your answer from them!