These 13" x 11" x 5" Corrugated Boxes have a thin corrugated wall designed for stacking strength. Box strength is measured using the Edge Crush Test (ECT); the corrugation used in these boxes can withstand 32 pounds per square inch (32 ECT). (Box contents should not exceed 35 lbs.) Boxes meet ASTM-D5118. For additional information on different box types and styles, view our Boxes and Mailers Comparison. Cartons are sold in bundle quantities and ship flat to save on storage space and shipping.