
Key Takeaways:
- You are creating ‘tangible’ marketing, so embrace it!
- Different form factors communicate your value prop in different ways
- Consider both size and emotional response when selecting form factors

Drive response with winning direct mail formats
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Your form factor is your campaign’s canvas. See what package types are proven performers when considering what to develop (and test) as part of your next effort.
There are a quad-zillion things marketers can test: offer, key message, brand elements, just to name a few. But one of the best tests in the realm of direct mail—and a testing strategy wholly unique to this ultra-tangible channel—is the format test.
No matter what other elements you test, your elements are communicated via a format. And on top of being the ‘first impression’ you make in the mailbox, each form factor allows you to communicate your offer—to tell your story—differently.
These six form factors have shown themselves to be tried-and-true performers, and serve as a great starting point for your next Direct Mail test:
Postcards

When you combine this form factor’s large size (usually 6”x9” or 6”x11”) with a killer offer, your piece is set up for success. On top of its size, this form factor instantly communicates both offer and CTA, since the recipient doesn’t have to open the piece to get to those nuggets. Not to mention, they are economical to produce!
Self Mailers

When you want the ‘billboard’ experience of a postcard but your story is bigger than just an offer and CTA, roll with a self-mailer. With multiple panels, your story can (literally) unfold, allowing you to incorporate more imagery and provide more detail.
Letter Packages

Why do so many DM format tests include at least one (if not many) letter packages? Because they can outperform other formats 2-to-1. Letter packs are economical to produce, and have a personal/official feel that encourages the prospect to take action. They are also one of the best form factors for stealth tactics. Be sure to consider an insert as part of the package.
Snap Packs

The official-looking snap pack is a great way to break through the clutter. Because this form factor traditionally carries must-read ‘institutional’ information, snap pack pieces are rarely left unopened. These are typically a lower-cost option to a letter package.
Invitation Packs

Want to convey upscale, friendly, or exclusive? Then you want to consider an invitation pack. No other form factor communicates ‘you’re special’ like this one. Invitation envelopes come in lots of different sizes, so when you combine the unique mailbox experience with the emotional response the form factor elicits, you’ve got a great package for the right campaign/offering.
Oversized Large Format Mailers

These big boys both sure do attract attention! With envelopes that are 9”x12” or more, they allow you to include detailed information—such data sheets and full-size brochures—and can also accommodate reply forms and business response envelopes. Again, because we as recipients are so accustomed to receiving ‘official’ information in large-envelope packages, these rarely go unopened, and are a great canvas for stealth elements.
And one final thought for y’all…
One of our key experiences with formats is that a change in form factor can breathe new life into a control package. Same messaging + different format = potential improved response on a control that’s showing fatigue!
Wanna talk form factors, messaging, or anything else DM-related? We’re standing by to answer any questions you might have—and most importantly—to help you get your mail opened. It’s as easy as dropping us a line.

Mike is the founder and president of Gundir, the award-winning direct marketing agency. Since 2003, Gundir has helped businesses drive new leads and close more sales through traditional offline channels, especially direct mail.
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