Solid 16 gauge steel 48 in and 36 in boxes. 20 gauge steel 30 in box. MIG welded seams for extra durability. Tamper proof locks keep tools safe. Recessed industrial strength handles. Heavy-duty locking hinge provides extra lid strength. Large and medium boxes are pre-drilled for casters (SKU 772.4156). Durable powder coat finish for rust-resistance and scratches.