Grip Seal Bags vs Mailing Bags: What's the Difference and When to Use Each

Both are polythene bags, both have a self-seal closure of some kind, and at a glance they might seem interchangeable. They're not. Grip seal bags and mailing bags are built for genuinely different jobs, and using one where the other is needed leads to either an item that's poorly protected or a parcel that doesn't seal properly for postage. Once you know what separates them, picking the right one becomes obvious.

This guide covers the practical difference between grip seal bags and mailing bags, and which one to reach for depending on what you're packaging.

The core difference

A mailing bag is an outer shipping bag. It's designed to be the final layer of packaging that goes through the postal system, with a permanent, tamper-evident self-seal strip intended for single use. Once sealed, it's not meant to be reopened and resealed in the way it was closed originally.

A grip seal bag is a resealable storage and organisation bag. It uses a press-to-close zip-style seal, similar to a sandwich bag, designed to be opened and closed repeatedly without losing its grip. It's built for containing and organising items, often as an inner layer of packaging rather than the final outer shipping layer.

That distinction, single-use shipping seal versus repeatable storage seal, is the main thing to keep in mind when deciding which one you need.

What mailing bags are for

Mailing bags are the standard outer packaging for shipping clothing, soft goods, accessories and similar items through the post. They're sized to fit garments and similar products, typically ranging from small bags suited to a single t-shirt up through large sizes for coats and bulky items. The film is opaque, which keeps contents private, and the self-seal strip is built to survive postal handling without opening accidentally.

If you're sending something through Royal Mail, Evri, DPD or any other UK courier, and the item is soft, flexible and doesn't need rigid protection, a mailing bag is almost always the right packaging. Our mailing bags range covers the full size spread most sellers need for clothing and general parcel dispatch.

What grip seal bags are for

Grip seal bags are built for smaller items that need to be contained, organised, kept dust-free, or protected from moisture, without necessarily being shipped as a standalone parcel. They're widely used for jewellery, small hardware and components, craft supplies, samples, and general organisation in both home and business settings.

The resealable nature is the key feature. Unlike a mailing bag's single-use seal, a grip seal bag can be opened and closed repeatedly without the seal losing its grip, which matters for anything you need to access more than once, such as a parts bin in a workshop, a sample kit that gets dipped into repeatedly, or jewellery that's tried on and put back before a sale goes through. Our grip seal bags range covers sizes from small enough for individual jewellery pieces up to small retail and sample sizes.

Can a grip seal bag be used to ship something through the post?

Not on its own, in most cases. Grip seal bags aren't designed with postal handling in mind the way mailing bags are. They're generally a lighter-gauge film, and the press seal, while genuinely reliable for repeated opening and closing, isn't intended to be the only thing holding a parcel together as it goes through sorting machinery and courier handling.

That said, grip seal bags work very well as an inner layer inside a mailing bag or box. If you're shipping small jewellery, components, or anything that benefits from being contained and protected from moisture or dust before it goes into the outer parcel, a grip seal bag inside the mailing bag is a sensible combination. The grip seal bag protects and organises the item itself; the mailing bag or box handles the outer shipping job.

Can a mailing bag be reused the way a grip seal bag can?

Not in the same way. A mailing bag's seal is designed to be tamper-evident, which means it shows clear signs of having been opened and generally doesn't bond with the same strength a second time. While a mailing bag can sometimes be reused for returns with a strip of tape over the resealed opening, it doesn't have the repeatable open-and-close function that a grip seal bag is built around. If you need something that opens and closes cleanly many times over, a grip seal bag is the right tool, not a mailing bag.

Choosing between them by use case

Here's a practical breakdown by scenario:

Using both together

For businesses selling small items such as jewellery, accessories, craft products or anything else that benefits from being individually contained, using a grip seal bag inside a mailing bag is often the best combination of the two. The grip seal bag keeps the item organised, protected from dust and moisture, and easy for the buyer to access and reuse if they want to. The mailing bag handles the outer shipping job, providing the tamper-evident seal and weather resistance needed for postal transit.

This layered approach is common practice among sellers handling small, valuable or delicate items, and it costs very little extra per parcel while giving a noticeably more considered unboxing experience than a single bag on its own.

The short answer

If you're shipping something through the post as a complete parcel, you want a mailing bag. If you're containing, organising or protecting something smaller, particularly something you might need to access more than once, you want a grip seal bag. For small valuable items being sold and shipped, using both together, grip seal inside, mailing bag outside, gives the best of both.

You can browse the full ranges on our mailing bags page and grip seal bags page. If you're not sure which combination suits what you're selling, get in touch and we can help you work it out.