Our heaviest mailing box — built from 3mm corrugated cardboard for items that need more protection than a standard mailer can offer. When you’re posting large, heavy, or fragile flat items and a standard 2mm mailer isn’t enough, the heavy-duty A3 mailing box delivers the extra rigidity and crush resistance to get it there in one piece.

3mm Board — The Thickest in Our Mailing Range

Standard mailing boxes use 2mm board. Our heavy-duty mailer steps up to 3mm corrugated cardboard — a significant increase in rigidity and edge crush resistance. The difference is felt immediately when you pick one up. For heavy books, framed certificates, mounted prints, and anything where a crushed corner isn’t an option.

A3 Format

Sized to fit A3 documents, prints, and flat products. The self-locking die-cut construction assembles quickly and holds its shape under the weight of heavier contents — no sagging, no bulging, no split corners.

Australian Made & Sustainable

Manufactured in Australia using sustainably sourced paper. 100% recyclable with a minimum 50% recycled content.