Our 9" x 9" x 13" Double Wall Corrugated Boxes are super strong and heavy duty 275# Double Wall/ECT-48 kraft corrugated carton with twice the protection of a standard carton. ECT stands for "edge crush test".ECT stands for "edge crush test". The 9 x 9 x 13 Double Wall Boxes with heavy-duty construction provides greater protection and is perfect to use when extra stacking strength is required. Perfect for shipping, storing or moving a wide variety of medium size items and tall products.