Use a corrugated box
Whenever possible, use a new box. The more times a box is used, the more it loses its original protective qualities, so a previously used box may not adequately protect your shipment and UPS may refuse a damage claim when using a previously used box.
If you must reuse a box, make sure it is rigid and in excellent condition with no punctures, tears, rips, or corner damage, and that all flaps are intact. Remove any old labels and shipment markings.
Choose a box strength suitable for the contents you are shipping. Never exceed the maximum gross weight for the box, which is usually printed on the Box Maker's Certificate on the box's bottom flap.