Superflat mailing boxes, also called flat mailing boxes, large letter boxes or rigid mailers, are slim corrugated boxes with about 16mm of internal depth. They protect cards, prints, photos, CDs, cosmetics and flat apparel far better than an envelope, yet stay thin and light to keep postage low. Choose from 14 sizes from 140 x 80mm to A3 440 x 320mm, in white, brown kraft, black, rose pink and mint blue, plus white tuck front versions.
Find your size
Eight superflat boxes drawn to the same scale, seen from above. Tap a box to shop it.
Superflat mailing box sizes and colours
| Inside (mm) | Colours & codes | Good for |
|---|---|---|
| 140 x 80 x 16 | B161 | Gift cards, jewellery, keyrings |
| 152 x 132 x 16 | B1B280B351 | CDs, cards, patches, stickers |
| 180 x 100 x 16 | B8B295B276B348B27 tuck | DL cards, phone cases, cosmetics |
| 192 x 125 x 16 | B10 | Cards, photos, small prints |
| 198 x 146 x 16 | B213 | A5 cards and booklets |
| 220 x 160 x 16 | B22B296B278B447B349B36 tuck | A5 prints, notebooks, flat apparel |
| 270 x 220 x 16 | B63 | Calendars, art prints |
| 280 x 192 x 16 | B109 | Books, planners, documents |
| 310 x 220 x 16 | B21B297B279B448B350 | A4 prints, certificates, flat clothing |
| 310 x 230 x 16 | B37 tuck | A4 items, premium tuck finish |
| 335 x 335 x 16 | B412 | 12-inch vinyl records |
| 350 x 250 x 15 | B9 | Large prints, documents |
| 360 x 250 x 20 | B102 | B4 documents and prints |
| 440 x 320 x 20 | B198 | A3 prints, posters flat, artwork |
Sizes are internal, length x width x depth. Tap a colour to shop that box. Going by post as a large letter? Check Australia Post’s current letter size and weight limits against the outside of the packed box.
Superflat mailing box FAQs ▾
Superflat mailing box FAQs
What is a superflat mailing box?
It is a slim diecut cardboard box with about 16mm of internal depth (15 to 20mm on a few sizes). It works like a rigid envelope that protects flat items from bending and crushing.
Can I post a superflat box as a large letter?
Often, yes. Australia Post sets size and weight limits for large letters, so measure the outside of your packed box and weigh it, then check the current limits with Australia Post before you post.
What fits in a 16mm superflat box?
Greeting and gift cards, art prints, photos, CDs, patches, stickers, phone cases, slim cosmetics, socks and flat-folded t-shirts.
What size superflat do I need for A4 or A3?
For A4 use 310 x 220 x 16mm (B21 and colours) or the 310 x 230 x 16mm tuck (B37). For A3 use 440 x 320 x 20mm (B198). B4 documents (250 x 353mm) fit the 360 x 250 x 20mm (B102).
Do you have a superflat box for vinyl records?
Yes. The B412 335 x 335 x 16mm fits a single 12-inch record. For several records, see the V6 LP record wrap.
Do you sell superflat boxes in bulk?
Yes. Packs range from 25 to 500, and wholesale cartons of the A4 (1,000), B4 (1,000) and A3 (400) sizes are available. See wholesale mailing boxes.
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