Expandable cardboard mailers adapt their depth to the product placed inside. A document can be shipped in a flat envelope, a book causes the sides to expand to its thickness, and a bulkier product opens the mailer further into a box-like shape.
These adaptable packs are also known as capacity mailers, gusseted cardboard envelopes or Amazon-style mailers. Their main advantage is simple: the packaging uses only the volume required by the product instead of leaving unnecessary empty space inside a standard box.
Expandable e-commerce mailers are manufactured from rigid cardboard or micro-flute corrugated board. Their folded side gussets remain flat when the contents are thin and open progressively when greater depth is required.
This creates a hybrid between an envelope and a box:
The mailer only expands within its designed dimensions. The product’s length, width and maximum thickness must therefore be considered when selecting the format.
The principal benefit is right-sized e-commerce packaging. The pack adjusts around its contents instead of forcing every product into a fixed-depth box.
This provides several practical advantages:
A small selection of adjustable-depth cardboard mailers can therefore cover a broader product range than the same number of fixed-size boxes.
These rigid cardboard mailers are particularly suitable for products with a relatively flat footprint but varying thickness, including:
Heavy, highly fragile, sharp or irregularly shaped products may still require additional protection or a conventional corrugated box. Packaging samples should always be tested with the intended products and distribution method.
Variable-depth mailers are most useful when the same packing operation handles products of different thicknesses. Their flat-to-box packaging design helps reduce void fill and avoids using a deep box for a thin item.
A standard box may remain preferable for heavy products, highly fragile goods, fixed-size items or applications requiring greater stacking strength. Flexible paper or plastic mailers may be sufficient for soft, non-fragile products where rigid protection is unnecessary.
The correct choice depends on the product dimensions, weight, protection requirements and shipping method.
Production begins with a suitably cut and creased cardboard blank. The blank is transported through the machine, where the expandable side gussets are formed and the permanent sections are folded and glued.
The mailer can also include:
The finished mailers are delivered ready for packing and expand only when a product with greater thickness is inserted.
The Manon envelope making machine is designed to manufacture micro-flute cardboard envelopes and thick cardboard mailers with expandable gussets.
A complete production configuration can include:
Manon processes open blank formats from 150 × 240 mm up to 780 × 700 mm and material weights from 200 to 600 g/m². The final configuration depends on the blank design, cardboard type, required expansion depth and selected closing system.
What is an Amazon-style mailer?
“Amazon-style mailer” is an informal market name for a rigid expandable envelope that can remain flat or open into a box-shaped pack. The format is also called a capacity mailer or expandable cardboard envelope and is not limited to one retailer.
Can one mailer fit products of any thickness?
No. One format can accommodate different thicknesses only within its designed capacity. The product must still fit the mailer’s usable length, width and maximum expanded depth.
Do expandable mailers eliminate all empty space?
They can significantly reduce unnecessary space because the gussets open according to the product’s thickness. However, fragile or irregular products may still require cushioning or other protective material.
Can these mailers include an adhesive closure and tear strip?
Yes. They can be produced as peel-and-seal mailers and can include an easy-open tear strip. The appropriate applicators depend on the chosen adhesive and opening system.
Send Macari Srl – Fidia your mailer sample or drawing, open blank dimensions, cardboard type, minimum and maximum filled depth, required closure features and expected production volume. We can evaluate the most suitable Manon configuration for your product.