When ordering 432 toothbrushes or more (6 boxes of 72 brushes per box = 432), then personalization is FREE. You can mix and match toothbrush styles (e.g. 3 boxes children's and 3 boxes of adult) to equal 6 boxes or 1 case and received FREE personalization. You just need 6 boxes/1 case of toothbrushes total. YOU MUST USE THE SAME IMPRINT ON ALL THE TOOTHBRUSHES TO GET FREE PERSONALIZATION. When ordering 5 boxes or less the personalization fee is a flat $20. Select "Yes" from the pull down menu below and you will be prompted on the next screen for your personalization options.