Heavy-duty double wall cardboard corrugated boxes 28″ x 28″ x 28″ 275#/ect-48 – 5 pack twice the protection of a standard carton. manufactured from heavy-duty 500# dw/ect-71 kraft corrugated heavy-duty construction provides greater protection and stacking strength ups rates these cartons up to 140 lb capacity cartons are sold in bundle quantities of 5 and ship flat to save on storage space and shipping for help selecting the right box, click the brochure tab below.