By viewing the 'Box Manufacturer's Certificate' (BMC) clearly printed on the bottom flaps, you will see the strength of the board, used to construct the box, as well as its size and weight limit.

 Also viewable in the seal is the Edge-Crush-Test or Burst-Test.

 Edge-Crush-Test (ECT) measures the stacking strength of corrugated cardboard boxes or fiberboard. Determining a finished box's compression-strength is defined by the amount of force that is needed to crush cardboard by standing it on its edge. This test is also measured in lbs.- per-square-inch. For example, a box with an ECT of 32 lbs.-per-square-inch indicates that the board, standing on edge, can withstand a force of 32 lbs.-per-square-inch before crushing. ECT = distribution & transportation of boxes and their stacking strength.

 Burst-Test (aka Mullen Test) is the force of pounds per square inch required to rupture - or burst - the side of a corrugated box. This method indicates the box's ability to withstand external or internal forces, and how the box will contain its contents during rough handling. For example, a box with a burst-strength of 200 lbs.-per-square-inch, indicates that the corrugated paper used to make the box can withstand 200 lbs. of pressure-per-square-inch.- The Burst Test = containment and handling ability of a box.