If I am envisioning your christening cake correctly, and your tier are 4" tall or more, I would suggest going with the 25mm.
© 2011-2015 CakesDecor.com. All Rights Reserved.
DISCLAIMER: Any posts on CakesDecor.com (CD) are posted by individuals acting in their own right and do not necessarily reflect the views of CD. CD will not be held liable for the actions of any user.