Poly bags / envelopes are usually made of three strong and lightweight layer film.
Three layers ,strong self-adhesive flap,has good function of waterproof.
And inner side is black or gray, the outer color could be white, gray or others.
The bag is designed an "one side flap" for protecting and deivery products.
Self sealing,lightweight, strong resistance to tear,customize printing.
Contact: email:cally@cnpacktech.com Tel: 13728853483