Depending on the package size there are 3 options that are most economical sense.
Padded Flat Rate USPS Priority Mail Envelope will hold 1 pair of adults or 6 fry.
Medium Flat Rate USPS Priority Mail will hold 6 pairs of young adults or 24 fry.
Large Flat Rate USPS Priority Mail 9 pairs of young adults or 36 fry.
![Trio of Tiger Endlers Packed in a Heat Sealed Kordon Breather Bag](https://livefins.com/wp-content/uploads/2014/03/tiger_trios_sealed_g2bags_001-800x600.jpg)
![Styrofoam liner installed within a USPS 6x7x7 Priority Mail Box](https://livefins.com/wp-content/uploads/2014/04/Package_001.jpg)