Quote Originally Posted by M. Lointain View Post
Substitute "masonite" for "cardboard" in ROL's post above and you will have a nearly indestructible package.
If you're anal.

As with many things photographic, experience will guide the degree of execution/protection/cost. Never had a cross-grain cardboard sandwich arrangement bend in the smaller sizes noted (a 4-ply matted print plus an 8-ply window mat is already fairly stiff at the core). AirFloat shipping packages have 1/4 inch plastic inserts on the inside of their units to prevent punctures, functioning better than masonite. Inexpensive plastic sheeting can be found at home stores to provide this extra protection should you desire it. But the weight of your package and shipping costs will increase dramatically (necessarily for large and multiple prints)