Box Liners 101: What They Are and How They Help in Bulk Packaging

When it comes to shipping or storing bulk goods, box liners offer one of the simplest and most cost-effective ways to protect products — and your packaging. 

From food-grade uses to industrial parts, a well-made poly liner helps ensure cleanliness, containment, and ease of transport. In this post, we’ll break down what box liners are, how they’re made, and why they’re a smart addition to many operations.

What Is a Box Liner?

A box liner is a clear poly bag placed inside a box, typically a corrugated case, to act as a barrier between the contents and the cardboard. At M Plastics Inc., we produce liners using LDPE blown film, custom-sized to match your box dimensions. 

Liners are usually: 

• Layflat bags, open-top, sized to fit standard or custom cartons 

• Bottom-sealed for strength and leak resistance 

• Packed loose or on rolls, depending on your packing style 

Once placed into the box, the liner can be folded over the product and sealed or simply tucked in. 

Why Use Box Liners?

Box liners serve multiple purposes: 

• Product Protection: Prevents moisture, dust, and contamination 

• Leak Control: Contains oils, powders, or fine particles that may seep 

• Clean Packaging: Reduces box staining or fiber shedding from recycled cartons 

• Compliance: Meets FDA or USDA requirements for food contact when needed 

• Reusable or Disposable: Depending on your process 

They’re essential in packaging resins, powders, grains, meat, bakery goods, bolts, soil, rocks, and more. 

How They’re Made at M Plastics

Our liners are made using the blown film extrusion process, giving us control over: 

• Gauge (thickness) — typically 1.5 to 6 mil 

• Opacity or Tint — clear, black, or colored 

• Additives — such as slip, anti-stat, or food-safe blends 

• Sizes — fully customized to your carton dimensions 

We can print liners with warnings, barcodes, or branding upon request.

Who Uses Them?

Box liners are widely used by: 

• Food processors and commercial kitchens 

• Manufacturers of powders, resins, and granules 

• Agricultural and landscaping supply companies 

• E-commerce fulfillment centers 

• Hardware and construction goods packagers 

In many industries, liners help reduce scrap, repackaging, and damage, especially in longer transit or storage situations. 

Final Thoughts: 

Box liners might seem like a small detail, but they play a big role in protecting your product and keeping your packaging clean. At M Plastics Inc., we work closely with clients to size liners properly, select the right gauge, and ensure they’re compatible with packing processes — whether by hand or automated. 

If your products ship in boxes, let’s talk about how the right liner can save time, reduce waste, and protect what matters.ct our team to explore liner options that align with your load sizes, stacking strength, and packing flow.