Mailer Box Inserts for Fragile Goods

Why do fragile items break inside a mailer box?

A parcel is dropped, stacked and tipped many times between your bench and the doorstep. Each knock pushes the product towards one wall. If there is a gap, the item picks up speed across it and hits the board hard.

Glass and ceramics usually crack at a corner or a rim, where the force lands on a small point. Two items packed loose together chip each other. A lid or pump top snaps when it is the part that touches the wall first.

An insert removes the gap. It holds the item in one place, keeps it off the walls and keeps separate pieces apart. Board choice matters too, but packing comes first.

What types of insert can go in a mailer box?

We make three kinds of insert, and each is quoted with the box so the sizes match.

• Die-cut board inserts: a flat sheet of corrugated board cut with holes or cradles shaped to the product, folded so the item sits raised off the base.
• Dividers: interlocking board strips that split the box into cells, so bottles or jars stand upright without touching.
• Paper void fill: crumpled or folded paper that fills the space around an item, useful for odd shapes and changing contents.
• Combinations: a die-cut cradle for the main item with paper fill packed around smaller extras.

Our insert fitted mailer boxes show how a cut board insert sits inside the box once folded.

Which insert suits which product?

The right insert depends on the shape of the item, how many pieces go in each box and whether the contents change from order to order.

How does a die-cut insert hold a jar or bottle?

A die-cut insert is cut from the same flat corrugated board as the box. The cutting die makes holes, slots and fold lines in one press, so every insert comes out the same.

For a jar, the insert usually folds into a raised platform with a round hole. The jar drops into the hole and the board grips it around the body. The base of the jar sits a little above the box floor, so a knock from below has board to pass through first.

For a bottle lying flat, the insert has two shaped notches, one for the shoulder and one near the base. The neck stays clear of the walls, which is where most bottles break.

How do you size an insert for a fragile product?

Insert sizing starts with the product, not the box. Get these steps right and the box size follows.

1. Measure the product at its widest point, including the lid, pump or handle.
2. Decide whether the item stands upright or lies flat. Standing usually suits jars; lying flat suits tall bottles.
3. Allow a snug fit in the insert hole, about 1 to 2 mm larger than the product.
4. Leave at least 15 mm between the product and each outer wall, filled by the insert.
5. Add the insert height to the product height to set the inside depth of the box.
6. Send us a sample product if you can, so we can test the fit before the proof.

Our guide on how to measure a mailer box covers product measuring in more detail.

Should you pair an insert with E-flute or B-flute?

Both boards work, and the box and insert do not have to match. A common pairing is a B-flute box for its thicker walls with an E-flute insert for neat, tight holes.

B-flute at 3 mm gives the box more cushioning between the product and the outside world. E-flute at 1.5 mm cuts cleaner, smaller shapes, which matters when the insert has to grip a narrow neck or a small vial.

The insert also adds stiffness to the whole parcel. A raised platform acts like an inner floor, so the box base and the insert both sit between the product and a knock from below.

Our guide comparing E-flute and B-flute sets out the differences between the two boards.

When is paper void fill enough?

Paper fill works well when the product is solid and simply needs keeping still. A wooden toy, a boxed gift or a stack of books can travel with paper packed firmly around it.

It is less reliable for glass and ceramics. Paper settles during the journey, and a jar that was held tight at packing can work loose by the time it arrives.

If you use it, pack it firmly on every side, including underneath. The lid should close with a slight press, without bulging.

A mix often works best. A die-cut cradle holds the fragile piece, and a little paper fills the corners around smaller extras such as a card or a sachet.

What packing mistakes cause breakages?

Most damage we see traces back to a few repeat habits on the packing bench.

• Sizing the insert to the product without its lid or pump, so the top touches the wall.
• Letting two glass items sit side by side without a divider between them.
• Leaving space above the item, so it bounces between the floor and the lid.
• Using paper fill alone for jars, then shipping in a box with room to spare.
• Changing the product, such as a new jar shape, without updating the insert.

Fix these and most breakages stop. A short test is worth it: pack one box, shake it gently and listen. Any rattle means something can still move.

Can an insert be printed?

Yes. Inserts can be plain kraft, plain white-lined board or printed to match the box. A printed insert turns the first look inside the box into part of the presentation.

Many sellers print a short line on the insert, such as a thank-you note or the name of each product beside its pocket. For gift sets and subscription box mailers, this replaces a separate card.

Keep the print simple on the parts that fold. Text near a crease can split, so place words on the flat top face of the insert where the customer sees them first.

How do you order a box with a fitted insert?

Send us the product sizes, how many items go in each box and whether you want the insert printed. A photo of the product helps us suggest the insert shape.

Boxes start from £0.25 a box, and the insert is priced on the same written quote, sent within one working day. A free design proof shows the box and insert flat and folded before anything is printed.

Production takes 4 to 6 working days after you approve the proof. Boxes and inserts arrive flat with free tracked UK mainland delivery in 2 to 3 working days. When ready, get a written quote for boxes.