6x9 poly mailers set of 100 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