Secure Seal: 6" x 4" x 3 Inches Mailers (Bulk 50 Pack) A better quality of boxes made with better materials. We use 32-ECT-B crush-resistant corrugated cardboard to create a lightweight, cheap-to-ship, die-cut box that's strong enough to stand up to whatever you need it to. Each box is rated for an ultra- durable 32-ECT-B crush resistance and gives you the most cost-effective way to ship your packages possible. All-Purpose These boxes are perfect for mailing, storage, moving, and organizers. They have amazing durability for shipping and stacking to ensure the safety of whatever you package. These folding boxes come together easily without tape, glue, or staples. They're totally foldable and are complete with double-walled sides. Secure Seal Secure Seal provides a huge variety of boxes in large and small sizes perfect for whatever you need. Check out our Amazon store for a full selection of boxes! We're dedicated to providing better products, that stand up better, at cheaper prices.