They do give you a chip to use for the race. You'll return it at the end, before you get too far from the finish, volunteers will snip it off your shoe. If you have your own chip, you can put the number in the registration and use it during the race. Which race are you doing?
Come join us on the walking/running club thread! There's several of us WISHers doing the Minnie race...at all levels from walkers to runners to woggers. We'd love to have you join us, but we may try to talk you into doing the DL or WDW half

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http://www.disboards.com/showthread.php?t=1055089