Airtite Holder For Large Cent?

Since the coin is 27.5mm which holder do you think would work better
a 27mm or 28mm.

Why do I ask?

I want to give a couple Large cents to my niece and nephew for a Christmas gift. So Finding something from 150 years older than the year that they were born, all that I could afford were a couple of "good" Large cents, but I want to put them in something nice when I give them to them. So I am going for the airtite in the velvet box.