Quality Park Survivor Shipping Envelopes are puncture, tear and moisture resistant so they can withstand the shipping process. These envelopes are made with durable 14 lb DuPont Tyvek, which is virtually indestructible, but still lightweight enough to save on postage costs. These 10" x 15" mailing envelopes have a Flap-Stik peel and seal closure which requires no moisture to seal and a release strip for quick, easy opening. Survivor Catalog Mailers provide a cost effective way to send important documents or re-sell items on an online marketplace so that recipients receive items intact. 100 per box. Tyvek is a trademark of DuPont used under license by LSC Communications US, LLC d/b/a TOPS Products.