Works with first class mail. Navy Blue Elephant Design outer surface/Grey inner lining - Metallic Gold Elephant print across both the front and back of each bag 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 100% recyclable,