A Sturdy Guide to Conformer Envelopes

Conformer envelopes are a little less well known than other envelopes. They are sturdy envelopes built to send large, heavy, or important items in the mail or around the office.

Consider any scenario when a regular padded envelope just won't do, but you don’t want to pay the added shipping costs associated with switching to a box. This may be to ship important documents, a stack of marketing materials, or a heavy book that could pierce through a regular padded envelope. Continue reading to learn all about conformer envelopes, including what to look for, what to use them for, and where you can buy them.


conformer envelopes

What is a Conformer Envelope?

The conformer envelope goes by many different names. They’re sometimes referred to as an expandable mailer, an expansion mailer, or a gusseted mailer, but any way you put it, conformer envelopes add stability to your mailing. The conformer envelope is made with sturdy materials that are meant to expand to fit larger items without damaging the envelope or its contents. 

They are generally made from a stiff paperboard that can withstand the sharp corners of items such as books, stacked marketing materials, or other bulky items. They will expand to hold several documents or larger items, becoming somewhat of a flat little box when filled. A conformer envelope needs to have a secure seal to keep heavier items inside. Often a Tyvek®binding is used on conformer envelopes because the adhesive is known for security and durability.


Why Choose a Conformer Envelope?

Conformer envelopes are ideal for shipping many items, but they may not be perfect in all cases. If what you are sending is not large, heavy, breakable, or important, consider using a regular padded envelope, as this will reduce waste and shipping costs. If bending is not a concern, and you only need to protect your shipping materials from pressure and water damage, you may want to consider a bubble mailer or a poly bubble mailer.

Choose a conformer envelope if you are shipping:

  • Pointed items that could pierce through other packaging materials
  • Heavy items that need durable packaging
  • Items or documents that cannot bend during shipping
  • Thick items or stacked materials that need more space than a regular envelope can handle


What to Look for in an Expansion Envelope

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Durability is of top importance for conformer envelopes. If you are choosing a conformer envelope, you know you need to protect what’s inside. Look for envelopes made with durable, water-resistant materials. For best results, conformer envelopes should be made from a stiff material that will hold its shape during shipping. Consider the corners of the envelope and look for any areas that could lose integrity, especially if you are shipping heavy or pointed items, such as books or CDs.

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Can the Conformer envelope expand to the dimensions you need? Expandability is important for conformer envelopes because they are used to fit larger items. Since the items are often important and valuable, the envelope must expand the fit all items comfortably. A stretched or tightly packed envelope of any kind will be more likely to break during shipping. A conformer envelope should expand and sometimes may have a gusset to fit larger items. These envelopes may be called gusseted mailers.

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Conformer envelopes need to have a secure, durable seal to contain the heavy items they often hold. Tyvek® seals are often associated directly with conformer envelopes because the binding is known for its durability. You will sometimes see conformer envelopes called tyvek expansion envelopes or tyvek expandable envelopes when they use a tyvek seal. Whether the seal is tyvek or not, it must securely close the conformer envelope and have long-lasting durability.

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Color and Texture

The standard conformer envelope texture is either kraft brown or white. They are available in other customized colors, but that is less common. Seek out an envelope color that matches your business’s branding if you want your envelope to stand out amongst other mail. A colored envelope can also spark joy for your customers when they receive your package in the mail.  

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Some online companies offer special customization at an increased cost. Customization comes in a variety of imprints, colors, and textures. Consider a customized printed or imprinted logo that will make your conformer envelope stand out while showing the world your company branding throughout the shipping process.

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The Right Size

Envelopes should never be filled to their maximum capacity. If you are struggling to fit what you need to ship, opt for a larger envelope or a conformer envelope that will expand to fulfill your shipping needs. A tightly packed, or stretched envelope has a higher chance of breaking while in the mail, so always ensure you have the right size for your mailing needs.

Conformer Expansion Envelope Uses

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Conformer envelopes are ideal for mailing both soft and hardcover books. The durability of the envelope can withstand the sharp corners of the books that might puncture a regular or padded envelope while in transit. The expandable size can fit larger books, and you never need to worry about the book being bent or dented in the mail.

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Conformer envelopes ensure that a magazine or multiple magazines stay protected during shipping. The stiffness of the conformer envelope will make sure the magazines don’t bend or dent in the mail.

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CDs, DVDs, and BluRays have thick packaging, and they are susceptible to damage in the mail. The sharp corners on CD cases may puncture through a regular or padded envelope. Conformer envelopes keep all types of media safe from damage while in transit.

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When mailing artwork, you need to ensure it does not bend or get damaged in any way. Conformer envelopes can protect prints, portfolios, calendars, and other artwork from being bent, scratched, or damaged by moisture in the mail. Protect your products and your own artwork with a sturdy conformer envelope.

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You might think that because clothing and other soft materials are flexible and light, they don’t need as sturdy of an envelope. Shipping soft materials in a regular paper envelope can lead to punctures and breakage of the packaging. If force is applied to the envelope, or if the point of a box or paperboard envelope reaches the regular paper, the package could puncture, leaving your shipping items vulnerable to damage.

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Marketing Materials

Conformer envelopes are perfect for shipping that in-between size—the size that’s not quite large enough for a box, but too large for a regular envelope. Large piles of marketing materials such as brochures, flyers, business cards, mailers, etc., are often shipped in conformer envelopes. They will keep marketing materials safe, flat, and dry during shipping, and it won’t cost as much as a cardboard box.

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Important Documents

Protect your important documents in conformer envelopes. Whether it be contracts, leases, certificates, diplomas, or any important documents, shipping them in conformer envelopes will ensure their security is maintained. Conformer envelopes will keep important documents safe from water damage or bending thanks to their durable material.


Where to Buy Conformer Envelopes

You won’t find conformer envelopes in any old stationary section. Look for conformer envelopes in stores that specialize in office supplies or shipping materials.

Unfortunately, conformer envelope options are scarcely available on Amazon, but they are available to purchase from a variety of online retailers that specialize in envelopes or shipping materials. If you want to include branded customization on your envelopes, search for “customizable conformer envelopes”to find a retailer that can meet your needs. 


    Envelope Guides From Blue Summit Supplies

    ✉️  An Ultimate Guide to Bubble Mailer and Padded Envelope Sizes

    ✉️  An Ultimate Guide to Poly Envelopes

    ✉️  A Sparkling Guide to Coin Envelopes

    ✉️  A Full Flap Guide to Remittance Envelopes

    ✉️  All About Tax Form Mailing: 1099 and W2 Envelopes


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    Jordan's passion for travel led her to design a career as a remote content marketer. Nearing 1000 published articles, she's spent the past decade using her interdisciplinary education to research and write content for a wide variety of industries. Working remotely, Jordan spends half of the year exploring different corners of the world. At home, she's content exploring fictional lands—Spark an immediate and detailed conversation by mentioning Game of Thrones, Red Rising, Star Wars, or Lord of the Rings.

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