When it comes to choosing a sleeping bag or quilt, fill power (FP) is one of the most commonly advertised specs—and one of the most misunderstood. It’s supposed to give you a clear picture of how light and lofty a down product will be, but the truth is some brands manipulate that number to have it look better on paper than it performs in real life.
Let’s break down what’s really going on—and how Zenbivy is doing things differently.
The Fill Power Loophole
Some companies take advantage of a legal but misleading loophole. The Federal Trade Commission allows brands to round fill power claims within 5% on natural products like down. That means a company with a down that tests at 950FP can legally call it 1000FP—even if the down has never come close to actually reaching that mark.
And it doesn’t just happen at 1000FP. This kind of rounding happens at every level. A product advertised as 900FP might really be closer to 860–880. You’ll pay a premium, but you won’t get exactly what you thought you were paying for.
Zenbivy Rounds Down—Not Up
At Zenbivy, we think this kind of marketing is misleading. That’s why we always round down on fill power claims. If our down tests at 920FP, we call it 900. If it hits 880, we list it as 850. We believe you should get at least what’s advertised—if not more.
You’ll never see us advertise “1000FP” down, because true, repeatable 1000 FP down does not exist at commercial scale. It’s a marketing myth, built on exaggerated rounding.
Transparency You Can Track
Want to be sure you’re getting what’s claimed? With Zenbivy, you can track your down and see the lab test results for yourself.
Our partner Allied Feather + Down provides Trace My Down hangtags with real test data for every lot of down we use. Just enter the lot number printed on your product tag at trackmydown.com to see the actual fill power, cleanliness, and sourcing info.
We’re also exploring ways to integrate down lot tracking directly into our website for even easier access.
What You Can Do
Ask for the numbers. If a company claims a certain fill power, ask them to provide the test results that back it up. If they can’t—or won’t—chances are the number was rounded up.
At Zenbivy, we’re committed to giving you real performance, not inflated numbers. Because when you're out in the backcountry, you deserve gear that lives up to the claim.
