They are polywoven or paper bags, constructed of level 1, level 2, level 3-4 or heavy - duty fabric with a polyethylene bladder used to restrain loads in rail cars, containers or trucks.
It is very important to place corrugated material or some other type of smooth surface on either side of the dunnage bag to protect it from rough edges (i.e. wooden crates, pallets, etc.).
Bags can burst with over inflation. (Each bag has a label with recommended pressure and filling instructions). Problems will be eliminated by following the installation instructions.