OEM Quality Park Plain Expansion Envelopes provide superior protection for mailing bulky items that are not too heavy. These regular-weight envelopes serve as an ideal replacement for costly boxes or cartons. Featuring an open-end style with a convenient Flap-Stik closure, they are made from durable DuPont Tyvek material that resists ripping, tearing, and puncturing. Water-resistant and moisture-resistant, these envelopes are easy to use with a simple peel and seal mechanism.