Extra Strength—For moderate use and higher stacking needs. Medium-duty box offers 30% greater stacking strength than other brands and is for storage with or without shelving. Easy one step FastFold™ set up. The 35% deeper lift-off lid stays in place to secure box contents. Smooth rolled box edges add strength and help prevent paper cuts. Global Product Type: File Boxes-Storage; Box Style: N/A; Box Type: Fast Fold™; Material(s): 1 Ply Side; 2 Ply Bottom; 2 Ply End.