Poly mailers are one of the most widely used shipping solutions in eCommerce; and for good reason. They're lightweight, flexible, water-resistant, and cost-effective. But they're not the right fit for every product. This guide covers what poly mailers are, how they work, and how to decide whether they're the right choice for your business.
What are poly mailers?
Poly mailers are flexible, lightweight shipping envelopes made from polyethylene: a type of plastic that's both durable and water-resistant. They're designed to ship directly without any additional outer packaging, making them a popular choice for eCommerce sellers who want to keep shipping costs low.
Unlike cardboard boxes or mailer boxes, poly mailers conform to the shape of the item inside. They typically feature a self-seal adhesive strip along the opening, so no tape is required to close them.
You'll recognize them easily: they're the soft, slightly crinkly envelopes that clothing orders and accessories often arrive in.
How do poly mailers work?
Poly mailers are simple to use:
- Place your item inside the mailer
- Peel the protective strip off the adhesive flap
- Press the flap down to seal
- Apply your shipping label to the front
Because they're flexible and lightweight, poly mailers compress around the contents, reducing the overall package volume. This matters for shipping costs, since carriers often charge based on dimensional weight; the heavier or bulkier a package, the more it costs to ship.
What are poly mailers made of?
Standard poly mailers are made from low-density polyethylene (LDPE), which gives them their characteristic flexibility and strength. The outer layer is typically smooth and slightly glossy, while the inner surface is softer to prevent scratching.
Most poly mailers are co-extruded, meaning two layers of polyethylene are bonded together during manufacturing. This construction makes them tear-resistant and harder to puncture than a single-layer plastic bag.
Some poly mailers include a grey or black interior lining, which adds an extra layer of opacity to keep contents private during transit. Higher-spec versions may include additional features like bubble lining for fragile items, or recycled materials for brands with sustainability goals.
Types of poly mailers
Not all poly mailers are the same. Here are the most common variants:
Standard poly mailers
The most widely used type: lightweight, smooth-exterior envelopes suitable for non-fragile items. Available in a wide range of sizes.
Bubble mailers
Poly mailers with a built-in bubble wrap lining. These offer more protection for items that are slightly delicate but don't warrant a full box: think jewellery, small electronics accessories, or cosmetics.
Biodegradable / compostable mailers
Made from plant-based materials rather than traditional polyethylene. A growing option for brands focused on sustainability.
Custom printed poly mailers
Standard or bubble mailers printed with your logo, brand colours, and messaging. These turn an otherwise plain envelope into a branded touchpoint.
When should you use poly mailers?
Poly mailers work best for products that are:
- Lightweight: they shine when shipping cost is tied to weight, as they add almost nothing to the total
- Non-fragile: the flexible exterior offers little protection against impact or crushing
- Non-rigid: soft or flexible items like clothing pack well; rigid products may be damaged if the mailer is squeezed during transit
- Not requiring a premium unboxing experience: poly mailers are functional, not aspirational
Common use cases include:
- T-shirts, hoodies, leggings, and other apparel
- Swimwear and athletic wear
- Scarves, socks, and lightweight accessories
- Documents and printed materials
- Small, durable accessories (phone cases, fabric pouches)
When should you choose something else?
Poly mailers aren't the right call for every shipment. Consider an alternative if:
Your product is fragile. Glassware, ceramics, electronics, and anything that can crack or break needs a rigid box, ideally with custom inserts, to survive transit safely.
Your product is rigid or boxy. Hard items like books, boxed goods, or products with protruding parts can puncture or deform a poly mailer during shipping.
Presentation matters. If you're selling premium products where the unboxing experience is part of the value, a custom mailer box or rigid box will do a much better job of communicating quality.
You need branded packaging with print on the inside. Custom mailer boxes can be fully printed inside and out, which creates a far richer unboxing experience than a poly mailer can offer.
Poly mailers vs. mailer boxes: which is right for you?
| Feature | Poly mailer | Corrugated mailer box |
|---|---|---|
| Weight added | Minimal | Moderate |
| Protection | Low (flexible) | High (rigid) |
| Branded print | Exterior only | Inside and out |
| Unboxing experience | Functional | Premium |
| Cost per unit | Low | Moderate |
| Best for | Soft, lightweight goods | Most eCommerce products |
For many eCommerce businesses, the answer isn't one or the other. Poly mailers for everyday lightweight orders, mailer boxes for higher-value or fragile shipments.
Can poly mailers be customized?
Yes. Custom printed poly mailers let you print your logo, brand colors, website, and any messaging directly onto the exterior of the mailer. This turns a plain plastic envelope into a recognizable brand experience: important when your packaging is the first physical thing a customer sees from your business.
Custom poly mailers are available in a range of sizes, colors, and finishes, with minimum order quantities that suit small businesses as well as established brands scaling their operations.
What to consider when choosing a poly mailer
Before ordering, think through:
- Size: The mailer should fit your product comfortably with a small margin: too large and the item shifts around; too small and you risk tearing the seal.
- Thickness: Measured in mils (thousandths of an inch). Thicker mailers (2.5 mil+) offer more durability for heavier items.
- Opacity: If you're shipping anything that shouldn't be visible from outside, choose a mailer with a grey or black interior lining.
- Sustainability: If eco credentials matter to your brand, look for mailers made with recycled content or certified compostable materials.
- Branding: Decide early whether you want plain or custom printed: custom orders require a minimum quantity and lead time.
The bottom line
Poly mailers are a practical, cost-effective shipping solution for eCommerce businesses sending soft, lightweight, non-fragile goods. They keep shipping costs down, store flat, and can be branded to reflect your business; making them a smart default for apparel brands and everyday online sellers.
If your product is fragile, rigid, or deserves a premium unboxing moment, a corrugated mailer box or premium shipping box will serve your customers better.
Not sure which shipping packaging is right for your products? Explore all custom shipping packaging options or get a sample kit to see and feel the difference before you commit.