How did you ship your disc to microsoft's disc replacement program?

Ok, it's getting down to the wire for me to ship in my highly scuffed Halo 3 disc for free replacement. Thing is, I'm not really sure how to go about this; when shipping a cd in standard mail, could I get away with sending them a slightly over sized envelope containing the cd, with a few first class stamps on top, or should I really go to the post office and pick up one of their small boxes to ship despite the elevated cost? What did you do? Thanks in advance! =)How did you ship your disc to microsoft's disc replacement program?I did not see any particular rules and/or regulations regarding how you should ship the item. I'd buy a cd mailer (they're probably like $1.50 and mail it with the form that way