Seashells Premium Poly Mailers 10x13 Pack of 25 USPS APPROVED FEDEX APPROVED UPS APPROVED Unsurpassed Water & Tear Resistance! Superior side seams combined with Heavy Duty polyethylene make these High Quality envelopes highly resistant to water, punctures, and tears. Pressure sensitive self seal. Easy packing, tamper-evident, and super secure closure. Light Weight & Time Saving! Lower shipping costs combined with faster shipment preparation equal big savings over other packaging option. 100% recyclable.