M4 Capacity Mailers 324x386mm Rigid Cardboard Envelopes Expandable Packaging Bags

M4 Heavy-Duty Expandable Kraft Capacity Mailers — Ultimate Protection for Bulky Shipments Smart Capacity Expansion & Heavy-Duty Build Say goodbye to oversized mailing boxes and fragile bubble bags. The M4 Solid Board Capacity Mailer is the ultimate fulfillment solution for online businesses looking to ship thicker items efficiently. Boasting flat dimensions of 324mm x 386mm, these premium wallets feature precision-engineered expandable side gussets. When loaded, they naturally pop open to comfortably handle deep profiles up to 312mm x 250mm x 70mm. This flexible depth makes them perfect for securely housing large books, tech accessories, catalogues, bound documents, textiles, and multi-item orders. Rigid Armor Protection & Security Constructed from premium-grade, rigid solid kraft board, the M4 mailer acts as a protective shield around your products. The tough, puncture-resistant material naturally resists bending, corner impacts, and rough transit handling, ensuring your items arrive at your customer's doorstep in pristine, retail-ready condition. Streamline your packing workflow with the integrated Peel & Seal flap. Backed by an industrial-strength, permanent self-adhesive strip, it forms a tamper-evident lock immediately upon contact—completely eliminating the need for expensive packaging tape. Seamless Unboxing Experience First impressions matter. The M4 mailer features a prominent, pre-scored perforated tear strip that allows your customers to pull and open their package cleanly in seconds. This prevents frustrated tearing or the use of sharp scissors, safeguarding the products inside from accidental damage. 100% Sustainable Eco-Branding Align your brand with eco-conscious consumer values. Every M4 mailer is prominently printed with standard recycling iconography and is 100% biodegradable, compostable, and recyclable. Made entirely from responsibly sourced natural kraft paper, it reduces your business's plastic footprint while delivering high-end, rustic professional presentation. Ideal Applications: Media & E-Commerce: Hardcover books, textbooks, thick catalogues, and annual reports. Retail & Apparel: Folded clothing items, soft goods, and textiles. Electronics & Office: Tablets, small framed items, components, and heavy stacks of legal or financial documents.