These heavy-duty, single- or double-wall, corrugated 275-lb boxes provide maximum protection to shipments. Approved for shipping via UPS, FedEx Ground, Parcel Post, truck, rail and express, the 275-lb corrugated packaging are shipped and stored flat. Extra-strong, single-wall 44-lb. edge crush test (ECT) boxes are 38% stronger than 200-lb. test packaging for greater crush- and puncture-resistance. Super-strong, double-wall 48-lb. edge crush test (ECT) boxes are twice as strong as 200-lb. test packaging for superior crush- and puncture-resistance, even during the roughest handling.