i'm using Brett's Safe Zone - http://www.biketoolmaker.com/Site/Sa...et_Mirror.html

costs an arm and a leg, but his implementation of industrial used Loc-Line for the links was ingenuous. plus his warranty support is stellar!

i must say i haven't used anything before, however this mirror makes it absolutely easy to see if your paceline (if you have company on a tour) are still sticking with you together in a line without turning your head!