ECT: edge crush test
ECT measures how much force the board can take on its edge before it crushes, in pounds per linear inch. It tells you how well a box stacks. 32 ECT is the most common single wall grade.
Mullen: burst test
The Mullen test measures how much pressure it takes to burst through the board, in pounds per square inch, and the box is called "200 lb test" or similar. It tells you how well a box resists rough handling and punctures. A 32 ECT single wall box is often compared with a 200 lb test box.
Which rating do you need?
If your boxes are stacked on pallets and in warehouses, stacking strength matters most, and ECT is the useful number. If boxes travel loose through parcel networks and get handled roughly, burst strength matters more. Your carrier's rules may also set a minimum.
Single wall or double wall
Single wall board has one fluted layer between two liners and covers most shipping. Double wall has two fluted layers and is used for heavier contents, tall stacks and rough handling.
The box maker's certificate
The certificate is the printed stamp on a box, usually on a bottom flap. It names the box maker and states the construction, the test the board meets, the size limit and the gross weight limit for that box.
Regular slotted containers
A regular slotted container, or RSC, is the everyday shipping box: all four flaps are the same length, and the outer flaps meet in the middle when closed. Box sizes are listed as inside length by width by depth.
What to send with a quote request
- Inside dimensions: length, width and depth
- The weight of what ships in each box
- How the boxes are stacked and shipped
- The rating printed on the box you use now
Sources: NMFTA: box manufacturer certificates; Industrial Physics (packaging test equipment maker): what is edge crush testing; FEFCO Code of Designs: style 0201, the regular slotted case.