If you are only shipping up to three babies then use an 8x8x8 box from "The UPS store" formerly known as MBE. Line all six sides with styrofoam sheeting. Secure geckos in deli cups (individually) with damp paper towel and surround containers with crumpled newspaper in the box so that they can not move around and are positioned in the center (just in case something happens to the box there will be some cushion). Of course the size of the gecko will determine the size of the deli cup and box.
Safe temps would be between 60-85, remember that the geckos will be inside a controlled temperature for the majority of the trip. If the temps are going to be outside of the listed temps you can use a heat or cold pack accordingly, or to be safe ship to the nearest UPS or USPS facility for pick up.
Hope this helps,
Uriah and Tina Walker
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