Can I add inserts to rigid set up boxes?

If you’ve ever placed a high-value item—say, a custom watch, a limited-edition vinyl record, or a precision tool—into a rigid set up box (RSB), you know that empty rigid corners and loose, shifting space don’t just feel unprofessional: they risk damaging the item during transit or storage. As a supplier of rigid set up boxes, one of the most common questions I hear from clients, from small e-commerce brands launching premium product lines to large retail teams restocking high-end inventory, is this: Can I add inserts to rigid set up boxes? Rigid Set Up Boxes

The short answer is yes, you absolutely can. But the “why” and “how” behind that answer is where most people get tripped up, especially when they’re working with pre-made rigid boxes or custom designs they already have in production. Over the 12 years I’ve been making rigid set up boxes, I’ve walked clients through dozens of insert projects—from simple foam cutouts for jewelry to custom die-cut cardboard trays for medical device prototypes—and the best results come from balancing three things: structural integrity of the rigid box, protection for your product, and cost-effectiveness for your operation.

Let’s start with the basics: what even is a rigid set up box? Unlike folding cardboard boxes (corrugated or paperboard that bends flat for shipping), rigid set up boxes are made with thick, sturdy materials—usually 2mm to 4mm paperboard cores, covered in fabric, leatherette, or premium paper finishes. They’re built to hold their shape, even when empty, so they’re popular for luxury packaging, corporate gifts, and items that need a premium unboxing experience. Their rigidity is their biggest selling point, which is why adding inserts feels like a potential risk: you don’t want to weaken the box’s structure, or have the insert shift and damage your product.

First, let’s address the structural question. A rigid box’s strength comes from its solid, non-bending sides and base, not from the interior space. Inserts work perfectly with this structure as long as you choose the right insert material and fit them correctly. For example, if you have a standard 10x8x3 inch rigid box with a base that’s ¼ inch thick, you can easily add a ¼ inch thick insert that fills the entire base, as long as it’s cut to match the box’s interior dimensions. The base’s rigidity will hold the insert in place, so it won’t shift during transit, and the insert itself will add a layer of cushioning for your product.

Where most new clients make a mistake is trying to use inserts that are too thick, or cutting them to overlap with the box’s lid. If your rigid box has a lid that sits ½ inch above the base, a ½ inch insert is fine, but if you try to make an insert that goes into the lid as well, you’ll risk warping the lid over time because the rigid box’s construction isn’t designed to bear pressure from both the base and lid. That’s a tip I learned early on: always keep inserts within the base of the box, not the lid, unless you’re working with a custom rigid box that’s built with extra internal supports.

Now, let’s talk about insert types, because not all inserts work the same with rigid set up boxes, and choosing the right one depends entirely on your product. I categorize inserts into four main types, and each has its own use case:

1. Corrugated Inserts: Thin, fluted cardboard that’s lightweight, affordable, and great for medium-weight products. I use these most often for e-commerce clients selling apparel accessories or small electronics. Corrugated inserts are easy to custom cut with a die, which means you can get a snug fit around your product without paying a premium. The fluted structure also adds a small amount of cushioning, which is good for products that don’t need heavy protection.

2. Foam Inserts: Open-cell or closed-cell foam, usually polyethylene, is the go-to for fragile, high-value items. For example, a client of mine that sells custom hand-blown glass ornaments asked me to add custom foam inserts to their rigid set up boxes to prevent chips during holiday shipping. The key here is to use a foam that’s soft enough to cradle the product but firm enough not to compress over time. I always recommend closed-cell foam for items that will be stored long-term, because open-cell foam can absorb moisture and get moldy in humid environments.

3. Die-Cut Cardboard Trays: These are similar to corrugated inserts, but made with thicker 2mm paperboard. They’re more rigid than corrugated, so they’re great for products that need more structure, like small tools or board game components. I’ve used these for corporate clients that give out custom USB drives as gifts; the die-cut tray holds the USB securely in place, and you can even print your brand logo on the tray for a cohesive look.

4. Custom Molded Inserts: For really unique, irregularly shaped products—like a vintage camera or a piece of jewelry with an unusual design—custom molded inserts (usually made of polyurethane or EVA foam) are the best option. These are molded to the exact shape of your product, so there’s zero chance of shifting. The only downside is that they’re more expensive than other insert types, so I only recommend them for high-value products where protection is non-negotiable.

Now, a common follow-up question: Can I add inserts to rigid set up boxes that I already have, or do I need to order new boxes? That’s a big one, and the answer is that it depends on the box. If you have a rigid set up box that’s in good shape—no warped corners, no dented sides—you can absolutely add inserts to it. I’ve done this for clients who ordered a bulk run of rigid boxes for a product launch, then decided at the last minute they needed inserts. All you need to do is measure the interior of the box (length, width, and depth of the base, not the lid), then order your insert cut to those exact dimensions. The only caveat is that if your box has a recessed base (some rigid boxes have a deeper base than the lid’s height), you’ll need to factor that into your insert measurement.

If you’re ordering new rigid boxes and inserts at the same time, there’s a huge benefit to doing this together: you can design the box and insert as a single unit, which leads to a tighter fit and better protection. For example, I worked with a luxury watch brand last year where we designed a rigid box with a base that’s slightly recessed, and a custom foam insert that fits exactly into that recess. The result is a box that feels seamless when you open it, with the watch sitting perfectly in place. That’s the kind of premium unboxing experience that makes customers come back, and it’s only possible when you coordinate the box and insert design.

Another thing to consider is assembly. Rigid set up boxes are shipped flat, right? Wait, no—actually, most rigid set up boxes are “set up” when they’re delivered, meaning they’re already folded into their final shape, not flat. That’s different from folding boxes, which you assemble yourself. So when you add inserts, you have two assembly options: you can add the insert after the box is set up, or you can add the insert during the box’s production. Adding it during production is usually better because it means the insert is fixed in place, so it won’t shift when you’re packing the product. If you add it after the box is set up, you’ll need a small amount of adhesive (usually double-sided tape) to hold it in place, which works fine, but it’s an extra step for your team.

Now, let’s talk about mistakes to avoid. I’ve seen clients make these three mistakes over and over, so I always warn them upfront:

First, don’t make the insert too tight. If your insert is cut to be even 1/32 inch smaller than the box’s interior, it will fit perfectly. If it’s too big, you’ll have to force it into the box, which can warp the sides of the rigid box and ruin its shape. I always recommend measuring twice and cutting once, especially with foam inserts, which can be tricky to trim down if you make a mistake.

Second, don’t use inserts that are too thin. A thin insert (less than ¼ inch) might not provide enough cushioning, and it can shift around the base of the box. For most products, I recommend a minimum of ¼ inch thick insert, and ½ inch for fragile items.

Third, don’t ignore the box’s finish. If your rigid box is covered in a delicate fabric or leatherette, make sure the insert material won’t scratch or stain it. For example, if you’re using a foam insert, make sure it’s a smooth, non-abrasive foam; rough foam can catch on the box’s finish and cause snags when you’re inserting or removing the product.

Let me give you a real example of a project we did recently to illustrate how this works. A client that sells premium wine accessories came to us last year, asking if they could add inserts to their existing rigid set up boxes for wine stoppers and pourers. Their boxes were 8x6x2 inches, with a black leatherette finish. We measured the interior of the base, then cut custom ¼ inch thick corrugated inserts with two die-cut slots: one for the wine stopper, one for the pourer. The inserts fit perfectly into the base, didn’t scratch the leatherette, and added just enough structure to keep the accessories from shifting during shipping. The client was able to use their existing box stock, so they saved money, and the finished product looked much more professional than loose accessories in an empty box.

At the end of the day, adding inserts to rigid set up boxes is not only possible—it’s one of the best ways to add value to your packaging. Inserts turn a plain rigid box into a functional, protective, and premium experience for your customers. Whether you’re a small business launching your first luxury product or a large corporation looking to upgrade your packaging, the key is to work with a supplier who understands both rigid box construction and insert design. They can help you choose the right insert material, design a fit that works with your existing boxes, and make sure the final product is both functional and beautiful.

If you’re ready to add inserts to your rigid set up boxes, or you have questions about custom designs, feel free to reach out. We’ve worked with all kinds of products, from small electronics to fragile art pieces, and we can help you find a solution that fits your needs and your budget. Don’t hesitate to get in touch to discuss your project.

Pulp Molded Packaging for Cosmetics References

1. Packaging Digest. (2022). Rigid Set-Up Boxes: Design and Construction Best Practices.
2. Custom Packaging Institute. (2021). Insert Materials for Premium Packaging: A Guide.
3. National Association of Printing and Packaging. (2023). Structural Integrity of Rigid Packaging and Inserts.
4. Luxury Packaging Association. (2022). Enhancing Unboxing Experiences with Custom Inserts.

Dongguang K.B.D Pulp Mould Package Products Co., Ltd.
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