You will find our poly mailing envelopes as most durable with exceptional puncture-resistance and tear-strength. These feature the self-seal adhesive closure which is tamper-evident & will not re-open once it has been closed properly. Moreover, on the surface, the labels & self stick stamps adhere securely and conveniently. These mailing bags are durable made with polyethylene film, are moisture-resistant and are opaque for privacy. These plastic mailing bags are lightweight but extremely strong for your needs.