Stylish Mustaches Poly Mailer 10x13 Pack of 20 MOVEMBER 100% Non-See Through, The Interior of our Multi-Layer Bags are Made with a Dark Lining Preventing the Contents of the Bag from Being Seen During Shipping. 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!