OEM Quality Park open-end expansion envelopes, sold in a carton of 100. These envelopes are made with heavyweight Tyvek, providing superior protection for mailing bulky items that are not too heavy. The open-end style features a convenient Flap-Stik closure, ensuring secure sealing. Water-resistant and moisture-resistant, these envelopes are much stronger than traditional paper options, making them ideal for various mailing needs.