Quote Originally Posted by KalEl View Post
It may be to keep/absorb moisture away from the item being sent, also can act as a charcoal filter type deal. As moisture can be an issue especially it sent by sea. The gravel/kitty litter is a great substance for this purpose.
I know that is done with paper/ceramic/porous substance items being shipped along sea routes, but if the rocks were in plastic bags, wouldn't that negate the absorbency gains?

Plus I doubt you'd ever need 1.8kg of kitty litter unless you were planning a bathroom break!