Purchasing this add-on will mean your stickers are shipped in a rigid cardboard mailer with a USPS tracking number. Without this add-on, all stickers ship untracked in a regular envelope by default.
 
This upgrade is for orders containing ONLY stickers! Orders containing any other items automatically come tracked, even if they include stickers along with the other items. You do not need to purchase this for any orders that contain more than stickers.