Tamper-Evident Postal Packaging Our M-D1/4 cardboard envelope mailer is a mid-small size in the Lil "M-Spec" range, purpose-built for small paperbacks, documents, and similar items that need more protection than a poly mailer but don't need a full box. Made from strong corrugated kraft cardboard, the M-D1/4 offers box-form rigidity in a slim, letterbox-friendly format. Pre-folded flaps and ghost creases mean fast, consistent packing every time, and the peel-and-seal tear-strip closure means you can seal orders without tape. Designed to accommodate Royal Mail's large letter tariff flat packed (180 x 265mm), or the small parcel tariff when expanded (181 x 110 x 70mm) — helping you keep postage costs down whichever way you pack it. (See our guide to large letter tariff savings for the full postage breakdown.) Our peel-and-seal closure uses a high-tack adhesive that bonds permanently on contact, unlike lower-security seals that can be carefully peeled back and reapplied without obvious signs of tampering. Once sealed, our mailers are tamper-evident: any attempt to open the parcel in transit leaves a clear, visible mark, giving your customers confidence that what arrives is exactly what was sent. Ideal for: small paperback books, documents, photo prints, greetings cards, and other small flat or lightly bulky items. Lil Packaging is Europe's largest independent producer of ecommerce postal packaging. See more of our M-Range Cardboard Mailers. Product Specification: Size: 180 x 265mm (flat pack) / 181 x 110 x 70mm (expanded) Material: Corrugated kraft cardboard Closure: Peel & seal, tamper-evident Postal fit: Royal Mail Large Letter (flat) / Small Parcel (expanded) Certifications: FSC®, Plastic Free, Zero Carbon Why choose the M-D1/4: 100% recyclable, FSC® certified, plastic-free Zero Carbon manufacturing (UK made) Peel-and-seal closure, no tape needed Reinforced corners reduce in-transit damage
