Custom Plain Mailer Boxes

Getting the Size Right on Plain Mailer Boxes

The biggest advantage of a custom plain mailer over a stock box is fit. A box that matches your product saves void fill, keeps the item from moving and can drop your parcel into a cheaper postage band. Measure the product or your typical bundle as packed, including any tissue or insert, and give us internal dimensions in length by width by depth.

Look at the postage bands for your carrier before deciding the depth. Large letter and small parcel sizes have limits on thickness, and a box just a few millimetres too deep can cost noticeably more to send. If your product is close to a limit, tell us and we will keep the box as slim as possible.

Most sellers find two or three sizes cover nearly all orders. Start with your most common order and add sizes once you see a real need.

Kraft or White, and Which Board

Brown kraft is the most popular plain mailer because it looks natural and honest, hides scuffs well and shows stickers and stamps clearly. White mailers look clean and modern, suit beauty and fashion brands, and give a brighter background for coloured stickers. White boxes do show marks from handling more easily, though.

For most products, E-flute corrugated board is the right weight: thin enough to fold neatly and keep the box slim, strong enough for courier networks. Heavier items or fragile goods suit B-flute, which is thicker and more crush resistant. Very light items, such as clothing or prints, can sometimes go in a heavy folding board mailer, which is slimmer still.

If you are unsure, order a small run of each and see which your customers respond to. Because there is no print to set up, switching colour or board on a later order is straightforward. The flute profiles and liners are described in our explainer on board and card types.

Styles and Useful Features

The roll end tuck front mailer is the standard shape: folded from one piece, with side flaps that lock into the lid and a front tuck that holds without tape. It assembles in seconds and looks neat. A version with dust flaps on the lid stops small items slipping out of the corners.

A peel-and-seal adhesive strip on the front flap removes the need for tape, which speeds packing and gives the box a tidy finish. A tear strip lets customers open the box cleanly and shows if it has been tampered with. A second adhesive strip allows the customer to reseal the box for returns, which is handy for clothing sellers. Where the lid should lock without a front tuck, the tuck top mailer boxes with locking ears are made from the same board.

Who Chooses Plain Mailers

Typical customers include new online shops, marketplace sellers, crafters and makers selling at markets and online, small subscription services in their first months, businesses running several brands from one warehouse, and companies that need a stock box for spare parts or samples. Some well-established brands keep plain mailers because they prefer the understated look.

Plain mailers are also popular for internal use: sending documents between offices, posting samples to clients or shipping parts to engineers, where branding is less important than a box that fits.

There is a practical reason too. Plain boxes are easier to reuse for returns, exchanges and replacements, because there is no campaign or date printed on them that could date them. Some sellers keep a small stock of plain mailers in each size purely for these jobs, alongside their main printed boxes. Most of them eventually choose a printed box from our shipping and mailer box range, using the plain box's dieline.

Get the Internal Size Right, Because Nothing Else Is Printed

With a plain mailer the only thing you are buying is fit, so spend the effort there. Measure the product as it will be packed, with tissue, a card and any bubble wrap, and add 5 mm to length and width and 3 mm to depth. Then check that outside size against the postal band you want; a plain box that lands in large letter instead of small parcel pays for itself quickly. Choose kraft unless stickers in pale colours are the plan, in which case white shows them better. Sellers who move on to print later keep the same dieline for the black mailer boxes with white print.

Email the internal size, board, quantity and any peel-and-seal or tear strip, and a custom quote comes back within one working day. A free proof still follows, showing the dieline with dimensions. Boxes are made in 4 to 7 working days after approval and arrive flat, free and tracked, on the UK mainland in 2 to 3 days. Crushed boxes reported within 10 days are replaced or refunded.