OEM Quality Park Lightweight Expansion Envelopes provide superior protection for mailing bulky items that are not too heavy. These envelopes are an ideal replacement for costly boxes or cartons, featuring an open-side style and convenient Flap-Stik closure. Made of DuPont Tyvek, they are much stronger and more secure than traditional paper envelopes, offering resistance to ripping, tearing, and puncturing. Additionally, these expansion envelopes are water-resistant and moisture-resistant, ensuring your items stay protected during transit.